A．Because they are not satisfied with their present jobs.
B．Because they are tired of the work.
C．Because they can’t cooperate well with their colleagues.
D．Because they want to earn higher degrees at the university.

A．Because she has been ill for a week.
B．Because she failed to pass the exam.
C．Because she had an unpleasant experience with a burglar.
D．Because she didn’t sleep well yesterday.