问题补充：
They peasants did what they the crops, but failed.
A. could save
B. could saving
C. could to save
D. could saved
答案：
A. could save
B. could saving
(答案→)C. could to save
D. could saved
解析：考查句子结构。从句what they could(do)作动词did的宾语，不定式to save the crops作全句的目的状语。防止误选A.
