He was instructed to act with extreme caution. 他被指示极其小心地行事。 The evidence of police informants needs to be treated with caution. 警方情报员搜集的证据应当得到慎重对待。 Researchers cautioned that the drug was only partly effective.研究者警告说，这种药只在一定程度上有效。 The judge cautioned them against taking the law into their own hands.法官警告他们不要玩弄法律。

2. prove （结果）表明；证明是（为系动词，无被动语态）;vt. 证明，证实 常用结构： prove (to be)+n./adj. （to be 可省去）证明是…… prove that-clause 证明…… prove sb.(to be)+n./adj. 证明某人是…… It is proved that ...据证明……