Question

英语语法题，选哪个？为什么？

The environment in my hometown is improving because many trees__________ every year.

A. plant B. are planted C. planted D. were planted

Answer 1

答案应该选B，are planted。
plant (种植)，及物动词。树应该被种，排除A和C。根据主句谓语动词 is improving 用了现在进行时态，排除 选项D，were planted(过去时)。

Answer 2

选B
every year一般现在时
trees作主语，谓语被动：被种
D和C是一般过去时，而A是主动的，都不合适。
我家乡的环境正在改善，因为每年种了很多树。