--Has your teacher returned from America yet?

--Yes, but he _______ here for only three days before his company sent him to Africa．

A．was

B．has been

C．will be

D．would be

数据专线验收测试记录表（互联网接入类）中，需要测试的项目包含下面哪些项？（）

A.平均时延

B.丢包率

C.带宽

D.网站浏览