问题补充：
---Your city looks beautiful. --- Yes. Lots of trees and grass last year.
A. are planted
B. have planted
C. were planting
D. were planted
答案：
A. are planted
B. have planted
C. were planting
(答案→)D. were planted
解析：句意：你们城市看来来很美丽。——是的，去年种了许多花草树木。结合语境可知下文描述的是过去某时发生的动作，故用一般过去时态。主语是动作对象，故用被动语态。选D。
