我丝毫都不怀疑我们对环境的污染是不可挽回的。I have no doubt that we are polluting the environment beyond redemption.我不怀疑那个女孩的真诚.I don't doubt the girl's sincerity.谁也不怀疑他适于担任这一职务.No one doubts his fitness for the position....

“不怀疑”的英语可以翻译为：implicity ...