Do you know how much time and effort they devoted such a complicated project?A. to complet

问题补充：

Do you know how much time and effort they devoted such a complicated project?

A. to complete

B. completed

C. completing

D. to completing

答案：

A. to complete

B. completed

C. completing

(答案→)D. to completing

解析：考查非谓语动词。定语从句的谓语动词与前面的先行词之间构成devote time and effort to doing sth.故答案为：D。