Amino axit X chứa a nhóm –COOH và b nhóm –NH₂. Cho 1 mol X tác dụng hết với dung dịch HCl thu được 169,5 gam muối. Cho 1 mol X tác dụng hết với dung dịch NaOH thì thu được 177 gam muối. Công thức phân tử của X là:

A. C₄H₇NO₄ 

B. C₅H₇NO₂ 

C. C₃H₇NO₂ 

D. C₄H₆N₂O₂ 

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 30 to 34.

Humans generally spent more time working than do other creatures, but there is greater variability in industriousness from one human culture to the next than is seen in subgroups of any other species. For instance, the average French worker toils for 1,646 hours a year; the average American for 1,957 hours; and the average Japanese for 2,088.

One reason for human diligence is that people, unlike animals, can often override the impulses they may feel to slow down. They can drink coffee when they might prefer a nap or flick on the air-conditioning when the heat might otherwise demand torpor. Many humans are driven to work hard by a singular desire to gather resources far beyond what is required for survival. Squirrels may collect what they need to make it through one winter but only humans worry about collect bills, retirement, or replacing their old record albums with compact discs.

Among other primates, if you don't need to travel around to get food for that day, you sit down and relax, said Dr.Frans de Waal of Emory University in Atlarita. "it's typically human to try to accumulate wealth and get more and more.”

Much of the acquisitiveness is likely to be the result of cultural training. Anthropologists have found that most hunter-gatherer groups, who live day to day on the resources they can kill or forage and who stash very little away for the future generally work only three to five hours daily.

Indeed, an inborn temptation to reduce may lurk beneath even the most work-obsessed people, which could explain why sloth ranks with lust and gluttony as one of the seven deadly sins.

According to the author, humans are so industrious because ______ 

A. they have an inborn temptation to take it easy so that they can survive

B. they are stronger and better protected than animals, so they can easily gain more to survive

C. they need much more than animals need in order to survive

D. they can overcome the impulse to slow down and they work for gains beyond survival

Thủy phân este có công thức phân tử C₄H₈O₂ (với xúc tác axit), thu được 2 sản phẩm hữu cơ X và Y. Từ X có thể điều chế trực tiếp ra Y. Vậy chất X là:

A. etyl axetat

B. ancol metylic

C. axit fomic

D. ancol etylic

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 38 to 42. Fill in the appropriate word in question 40

        The popular image of student life is of young people with few responsibilities enjoying themselves and (38) _____ very little work. This is often not true. Many older people now study at college or university, sometimes (39) _____ a part-time basis while having a job and looking after a family. These students are often highly motivated and work very hard.

        Younger students are often thought to be lazy and careless about money (40) _____ this situation is changing. In Britain reduced government support for higher education means that students can no longer rely on having their expenses paid for them. Formerly, students received a grant towards their living expenses. Now most can only get a loan (41) _____ has to be paid back. Since 1999 they have paid over £1,000 towards tuition fees and this amount will increase up to a maximum of £3,000. In the US students already have to pay for tuition and room and board.

        Many get a financial aid package which may include grants, scholarships and loans. The fear of having large debts places (42) _____ pressure on students and many take part-time jobs during the term and work full-time in the vacations.

A. and

B. or

C. so

D. but

Amino axit X có 1 nhóm -NH₂. Cho 0,01 mol X tác dụng vừa đủ với 200 ml dung dịch NaOH 0,1M. Mặt khác, khi cho 0,03 mol X tác dụng với 40 gam dung dịch NaOH 7,05%, cô cạn dung dịch sau phản ứng thu được 6,15 gam chất rắn. Công thức của X là 

A. H₂NC₂H₃(COOH)₂

B. H₂NC₃H₅(COOH)₂

C. H₂NC₄H₇(COOH)₂

D. H₂NC₅H₉(COOH)₂