1. They always perform their duties faithfully.
    他们总是忠实地履行自己的职责。

2. He loved to be told that one of his imaginary products was temporarily out of stock and he would faithfully promise to call again at some future date, but of course he never did.
    他爱听售货员说他想像出来的那种东西暂时脱销，于是他就煞有介事地许诺改天再来光顾。当然，他再也不会来了。