I told Sally how to get here, but perhaps I for her.
A. had to write it out
B. must have written it out
C. should have written it out
D. ought to write it out
网友回答
A. had to write it out
B. must have written it out
(答案→)C. should have written it out
D. ought to write it out
解析：根据句意“我已经告诉她怎样到那儿，但是或许我应该给她写下来”可知，说话者含有“后悔、遗憾”的意味，应使用“情态动词+完成式”形式，“must+完成式”表示对过去的肯定推测，“should+完成式”才表示虚拟意义。