2013年自考《英语（二）》每日一练

单选题

1.In the original test，all the animals in a test group are given a substance _______ half of them die.

A.unless

B.until

C.lest

D.provided

正确答案：B

答案解析：本题考查词义辨析。until：直到。符合句意，表示given a substance持续到half of them die。