题干
-- Hello, may I speak to Mr Smith?
-- Sorry, he isn't in. He the office.
A：has been to
B：has gone to
C：has been away
D：has gone away
答案(点此获取答案解析）
B
-- Hello, may I speak to Mr Smith?
-- Sorry, he isn't in. He the office.
A：has been to
B：has gone to
C：has been away
D：has gone away
为电池充电时，与外电源正极连接的电极上发生的反应是