Question

He _____ when the UFO arrived.         
A. was sleeping   B. were sleeping       C. has slept

Answer 1

A

考查时间状语从句。句意“当UFO来时，他正在睡觉。”he是第三人称，故谓语用单数，排除B；根据arrived可知，用过去式，排除C。故选A。