The magician picked several persons from the audience and asked them to help him with the

问题补充：

The magician picked several persons from the audience and asked them to help him with the performance.

A. by accident

B. on occasion

C. at random

D. on an average

答案：

A. by accident

B. on occasion

(答案→)C. at random

D. on an average

解析：at random(=without aim or purpose)随便地，胡乱地：His clothes were scattered about the room at random.

By accident意外地；on occasion偶尔；on an average平均计算。