I’m most awfully grateful to you. I can’t think what I without you.
A. could do
B. would do
C. should have done
D. must have done
网友回答
A. could do
B. would do
(答案→)C. should have done
D. must have done
解析：考查情态动词。句意：我非常的感激你，我认为没有你我本不应该完成的。should have done 本应该做某事而事实上没有做，shouldn’t have done 本不应该做某事而实际上做了。所以选C。