Accordingtothereport,thenumberofanimalsusedinexperimen...

问题详情：

 According to the report, the number of animals used in experiments _______by 30% over the years.

A. was reduced               B. has been reduced      C. were reduced             D. have been reduced

【回答】

B

知识点：现在完成时及其被动式

题型：选择题