题目

以下不能合成ATP的细胞或结构是（ ） A . 人体成熟的红细胞 B . 噬菌体 C . 叶绿体 D . 大肠杆菌 答案：B27、---Has your father returned from Africa yet? ---Yes, but he ____ here for only three days before his company sent him to Australia． A．was           B．has been         C．will be         D．would be