The magician picked out several persons______from the audience and asked them to help him with the performance.
【正确答案】 D
【答案解析】本题空格处是说魔术师从观众中随意选了几人。D项at random“随意地”符合题意。其他三项by accident“偶然”，on average“平均起来”，on occasion“有时”都不正确。