--- Hello! Is Mr. John in the office?
--- Yes. But I’m sorry. He is busy and can’t speak to you.
A. at once
B. at present
C. at the end
D. at first
网友回答
A. at once
(答案→)B. at present
C. at the end
D. at first
解析：词义辨析。A立刻，马上；B现在；C最后；D起初。句意：—你好，Mr John在办公室吗？—是的。但是对不起。他现在很忙，没有时间和你说话。故B正确。