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.

Legend has it that sometime toward the end of the Civil war (1861 – 1865) a government train carrying oxen travelling through the northern plains of eastern Wyoming was caught in a snowstorm and had to be abandoned. The diver returned the next spring to see what had become of his cargo. Instead of the skeletons he had expected to find, he saw his oxen, living, fat and healthy. How had they survived?

The answer lay in the resource that unknowing American lands trampled underfoot in their haste to cross the “Great American Desert” to reach lands that sometimes proved barren. In the eastern parts of the United States, the preferred grass for forage was a cultivated plant. It grew well with enough rain, then when cut and stored it would cure and become nourishing hay for winter feed. But in the dry grazing lands of the west that familiar bluejoint grass was often killed by drought. To cattle out there seemed risky or even hopeless.

Who could imagine a fairy-tail grass that required no rain and somehow made it possible for cattle to feed themselves all winter? But the surprising western wild grasses did just that. They had wonderfully convenient features that made them superior to the cultivated eastern grasses. Variously known as buffalo grass, grama grass, or mesquite grass, not only were they immune to drought; but they were actually preserved by the lack of summer and autumn rains. They were not juicy like the cultivated eastern grasses, but had short, hard stems. And they did not need to be cured in a barn, but dried right where they grew on the ground. When they dried in this way, they remained naturally sweet and nourishing through the winter. Cattle left outdoors to fend for themselves thrived on this hay. And the cattle themselves helped plant the fresh grass year after year for they trampled the natural seeds firmly into the soil to be watered by the melting snows of winter and the occasional rains of spring. The dry summer air cured them much as storing in a barn cured the cultivated grasses.

The word “barren” in paragraph 2 is closest in meaning to _________.

A. lonely

B. uncomfortable

C. infertile

D. dangerous

Các ion nào sau không thể cùng tồn tại trong một dung dịch?

Cho các phát biểu sau:

(1) Nitơ thuộc nhóm VA, chu kì 2

(2) Trong phân tử nitơ có chứa một kiên kết ba

(3) Trong điều kiện thường, nitơ là chất lỏng, không màu, mùi xốc, nhẹ hơn không khí

(4) Nitơ không duy trì sự cháy và nitơ tan nhiều trong nước

(5) Ở nhiệt độ thường, nitơ hoạt động hóa học mạnh và có thể tác dụng với nhiều chất

(6) Nitơ vừa có tính oxi hóa vừa có tính khử

Số phát biểu đúng là

A. 2

B. 3

C. 5

D. 4

Nêu định nghĩa đoạn [a; b], khoảng (a; b), nửa khoảng [a; b), (a; b], (-∞; b], [a; +∞). Viết tập hợp R các số dưới dạng một khoảng.

Mark the letter A, B, C or D on your answer sheet to indicate the word(s) CLOSET in meaning to the underlined word(s) in each of the following questions.

Rearrange the following sentences to make a letter of acceptance responding to an invitation to spend a weekend in the country.

A. Rebuke

B. disparagement

C. dislike

D. refusal