单选题 The laboratory technician often warns the trainees that they can't be______careful in doing the experiment.
【正确答案】 D
【答案解析】[分析] cannot…too无论怎样……也不过分,在此结构中,cannot也可改用can hardly/scarcely/never/impossible,too可以改用over, enough, sufficient,如:We can hardly praise his achievement too much.对他的成就我们无论怎样赞扬也不过分。A man can never have too many friends. 朋友越多越好。