students took the high school entrance exam on time the morning of June 16th in Yancheng

问题补充：

students took the high school entrance exam on time the morning of June 16th in Yancheng , though it rained heavily .

A. Thousands of ; in

B. Many thousands ; on

C. Thousands of ; on

D. Thousand of ; on

答案：

A. Thousands of ; in

B. Many thousands ; on

(答案→)C. Thousands of ; on

D. Thousand of ; on

解析：句意：虽然羊城在6月16日早上下了很大的雨，但是数以千计的学生按时参加了高中入学考试。thousand意为“一千”，当其前面有具体的数目时，不能加s;但泛指许多时，则用复数，且常和介词of连用，构成短语thousand of,意为“成千上万的、数以千计的”，排除B、D，在具体某天的早、午、晚用介词on，故选择C。