Trộn dung dịch chứa 1 mol H₃PO₄ với dung dịch chứa 1,5 mol NH₃. Tính khối lượng amophot được tạo thành. Giả sử hiệu suất phản ứng đạt 95%.

A. 123,5 gam

B. 117,325 gam

C. 93,86 gam

D. 128,5 gam

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 36 to 42.

Life originated in the early seas less than a billion years after the Earth was formed. Yet another three billions years were to pass before the first plants and animals appeared on the continents. Life's transition from the sea to the land was perhaps as much of an evolutionary challenge as was the genesis of life.

What forms of life were able to make such a drastic change in lifestyle? The traditional view of the first terrestrial organisms is based on megafossils - relatively large specimens of essential whole plants and animals. Vascular plants, related to modern seed plants and ferns, left the first comprehensive megafossil record. Because of this, it has been commonly assumed that the sequence of terrestrialization reflected the evolution of 10 modern terrestrial ecosystems. In this view, primitive vascular plants first colonized the margins of continental waters, followed by animals that fed on the plants, and lastly by the animals that preyed on the plant-eaters. Moreover, the megafossils suggest that terrestrial life appeared and diversified explosively near the boundary between the Silurian and the Devonian periods, a little more than 400 million years ago.

Recently, however, paleontologists have been taking a closer look at sediments below this Silurian- Devonian geological boundary. It turns out that some fossils can be extracted from these sediments by putting the rock in an acid bath. The technique has uncovered new evidence from sediments that were deposited near the shores of the ancient oceans - plant microfossils and microscopic pieces of small animals. In many instances, the specimens are less than one-tenth of a millimeter in diameter. Although they were entombed in the rocks for hundreds of millions of years, many of the fossils consist of the organic remains of the organism.

These discovered fossils have not only revealed the existence ofpreviously unknown organisms, but have also pushed back these dates for the invasion of land by multicellular organisms. Our view about the nature of the early plants and animal communities are now being revised. And with those revisions come new speculations about the first terrestrial life-forms

The word "extracted" is closest in meaning to ___________.

A. located

B. preserved 

C. removed

D. studied

Read the passage and choose the best option to complete each blank.

        Any change in one part of an ecosystem can cause changes in other parts. Droughts, storms and fires can change ecosystems. Some changes ____46___ ecosystems. If there is too little rainfall, plants will not have enough water to live. If a kind of plant dies off, the animals ____47___ feed on it may also die or move away. Some changes are good for ecosystems. Some pine forests need fires for the pine trees to reproduce. The seeds are sealed inside pinecones. Heat from a forest fire melts the seal and lets the seeds ____48___. Polluting the air, soil, and water can harm ecosystems. Building dams on rivers for electric power and irrigation can harm ecosystems ____49___ the rivers. Bulldozing wetlands and cutting down forests destroy ecosystems. Ecologists are working with companies and governments to find better ways of ___50____ fish, cutting down trees, and building dams. They are looking for ways to get food, lumber, and other products for people without causing harm to ecosystems.

Điền vào số (47)

A. who                 

B. where               

C. that  

D. when

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 36 to 42.

Life originated in the early seas less than a billion years after the Earth was formed. Yet another three billions years were to pass before the first plants and animals appeared on the continents. Life's transition from the sea to the land was perhaps as much of an evolutionary challenge as was the genesis of life.

What forms of life were able to make such a drastic change in lifestyle? The traditional view of the first terrestrial organisms is based on megafossils - relatively large specimens of essential whole plants and animals. Vascular plants, related to modern seed plants and ferns, left the first comprehensive megafossil record. Because of this, it has been commonly assumed that the sequence of terrestrialization reflected the evolution of 10 modern terrestrial ecosystems. In this view, primitive vascular plants first colonized the margins of continental waters, followed by animals that fed on the plants, and lastly by the animals that preyed on the plant-eaters. Moreover, the megafossils suggest that terrestrial life appeared and diversified explosively near the boundary between the Silurian and the Devonian periods, a little more than 400 million years ago.

Recently, however, paleontologists have been taking a closer look at sediments below this Silurian- Devonian geological boundary. It turns out that some fossils can be extracted from these sediments by putting the rock in an acid bath. The technique has uncovered new evidence from sediments that were deposited near the shores of the ancient oceans - plant microfossils and microscopic pieces of small animals. In many instances, the specimens are less than one-tenth of a millimeter in diameter. Although they were entombed in the rocks for hundreds of millions of years, many of the fossils consist of the organic remains of the organism.

These discovered fossils have not only revealed the existence ofpreviously unknown organisms, but have also pushed back these dates for the invasion of land by multicellular organisms. Our view about the nature of the early plants and animal communities are now being revised. And with those revisions come new speculations about the first terrestrial life-forms

The word "drastic" is closest in meaning to ________.

A. widespread

B. radical

C. progressive

D. risky

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from .

           Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it.

          M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites.

M.L. was _______ by the atmosphere in which he grew up.'

A. not affected at all

B. doubted

C. certainly influenced

D. prejudiced