Question

The days are gone ________ we could leave our door unlocked at night.

A．where

B．which

C．when

D．while

Answer 1

C

考查分割式定语从句。先行词为the days，谓语是are gone，后面的从句不缺少主语或宾语，缺少时间状语，所以使用关系副词。故选C。