急性毒性研究的接触时间是（）。
A.一次
B.一次或8小时以内
C.一次或24小时以内
D.一次或7天以内
E.一次或14天以内
参考答案：C
巫术说
We have been told that under no circumstances we can use the telephone in the office for personal affairs.
A. did we use B. may we use C. we may use D. we could use
