问题补充：
In order to make our city green，.
A. it is necessary to have planted more trees
B. many more trees need to plant
C. our city needs more trees
D. we must plant more trees
答案：
A. it is necessary to have planted more trees
B. many more trees need to plant
C. our city needs more trees
(答案→)D. we must plant more trees
解析：此题考查动词不定式的逻辑主语。句意：为了绿化我们的城市，我们必须种植更多的树。显然，“绿化城市”的动作是句子的主语发出的，所以只能是D项。本句可改为：We must plant more trees so that we can make our city green.
