Question

Mr. Green _______ his lessons when I went into his office.

A．prepares	B．prepared
C．is preparing	D．was preparing

Answer 1

D

试题分析：句意：格林老师在我走进他办公室时他正在备课。when从句中用的是一般过去时态，所以根据句意主句应用过去进行时态，故选D。