By the time my parents reached home yesterday I the dinner already.A. had cookedB. cooke

问题补充：

By the time my parents reached home yesterday, I the dinner already.

A. had cooked

B. cooked

C. have cooked

D. was cooked

答案：

(答案→)A. had cooked

B. cooked

C. have cooked

D. was cooked

解析：在英文中有by the time构成的时间状语从句，主句通常用过去完成时，结构为had+过去分词，故本题选A。