It’s hard for us to make a choice, which means we have not decided .
A. to take a step
B. to take which step
C. which step to take
D. to take what
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A. to take a step
B. to take which step
(答案→)C. which step to take
D. to take what
解析：本题考查非谓语动词。which step to take是疑问代词+不定式的用法，表示“采取哪一步”。句意：选择对我们来说很难，意味着我们还没有决定将采取哪一步。