The bus came after I ( ) for about half an hour.

A.had been waiting
B.have waited
C. had been waited
D.was waiting
出自:当代英语语法概论

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