单项选择题
I（）half an hour before she came out of the telephone box and I entered.
A．waited B．have waited C．had been waiting D．was waiting
单项选择题 Koalas(考拉熊) use a range of sounds to communicate with one another（）relatively large distances.
单项选择题 The mother didn't know who（）for the broken window.
单项选择题 （）the cause, they were able to propose to a remedy.
