11.   Raise your hand if you know the right answer.

12.   The body clock has been studied very little in older volunteers and so we do not know the answer to this.

13.   The cleverest girls always knew the answer of course.

14.   To know the answer to that would have been really interesting.

15.   We all know the answer to this whodunit.

16.   When she asked Karen a question, even though Karen knew the answer her mind immediately went blank.

17.   Not one of the students knew the answer.

18.   Who knows the answer?

19.   Raise your hand if you know the answer.

20.   He bombarded Catherine with questions to which he should have known the answers.