over and over again,but he still couldn.t understand.
A.Having explained
B.Having been explained
D.It had been explained
C.Explaining
出自:专升本英语

完成拼图验证

按住下方滑块,将拼图拖到缺口处后松开。

拼图背景,将小拼图拖到缺口处
向右拖动滑块