问题补充:
Trees every year to make our city greener.
A. plant
B. are planted
C. were planted
D. will be planted
答案:
A. plant
(答案→)B. are planted
C. were planted
D. will be planted
解析:本题的含义是每年我们要栽许多的树,本题表示的是一般的情况用一般现在时,主语树为动作的承受者,故本题使用一般现在时的被动句,结构为be+过去分词,本题的主语是复数,故本题选B。