Question

【题目】Every year thousands of trees _________ to improve the environment.
A.were planted
B.are planted
C.have planted
D.will plant

Answer 1

【答案】B
【解析】句意为：为了提高环境，每年要植成千上万的树。tree是动作plant的承受者；故应用被动语态。由every year可知此句为一般现在时，故选B。