Accordingtothereport,thenumberofanimalsusedinexperimen...

問題詳情：

 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

知識點：現在完成時及其被動式

題型：選擇題