单选题 Answering mobile phone calls while you are at a work meeting is not only discourteous, but it can also destroy the ______ of the meeting.

【正确答案】 B

【答案解析】会议中接听电话不仅是一种没有礼貌的行为，而且会影响会议的顺利进行。最符合句意的是(B)efficacy(效率，功效)。