Ladies and Gentlemen, please remain   until the plane has come to a complete stop. 

Professor Li preferred _______ lectures to his students to _______ to meetings on scientific developments.

Tom pretended______it but in fact，he knew it very well.

There is no need ______ because Mr. Smith is still sleeping.

On his way home, he found a wallet ___ on the ground, which he picked up and ____ in his schoolbag.