问题补充：
I’m sorry that I can’t help trees because I am busy with the homework.
A. to plant
B. planting
C. planted
D. plants
答案：
(答案→)A. to plant
B. planting
C. planted
D. plants
解析：词组辨析题。can’t help to do sth 不能帮助做某事； can’t help doing 情不自禁做某事。句意：很抱歉我不能帮你种树因为我忙着写作业。选A
