As an experienced teacher, your teaching methods have to be _________enough to meet the demands of different students.

Whenever we try to do something and fail, we always end up ____ something else.— Oh, that`s the reason why you can`t succeed.

Ladies and gentlemen, please remain _____ until the plane has come to a complete stop [ ]

She advised me ________ English with foreigners.

is known to us all isthe old scientist, for whom life was hard in the past, still works very hard in his eighties.