By the time my mother came back from work, my sister and I       supper and wer

题型：不详难度：来源：

By the time my mother came back from work, my sister and I       supper and were waiting for her at the table.

A．have cooked

B．were cooking

C．had cooked

D．would cook

答案

C

解析

在英文中用by the time构成的从句修饰主句，主句通常用过去完成时，结构为had+过去分词，故本题选C。