Millions of treeson March 12th last year.A. are plantedB. were plantedC. was plantedD. is

问题补充：

Millions of treeson March 12th last year.

A. are planted

B. were planted

C. was planted

D. is planted

答案：

A. are planted

(答案→)B. were planted

C. was planted

D. is planted

解析：考查被动语态, 根据last year确定时态为一般过去时态，其次根据trees确定出be动词的单复数。“去年的3月12日数以百万计的树木被种植。”