As a teacher, I seldom give my students so difficult a problem_______ they can’t work out.
She ought to stop working; she has a headache because she _________ too long.
-Not getting that job was a big disappointment. -Don’t worry. Something better will ________.
The man we followed suddenly stopped and looked as if _________ whether he was going in the right direction.
-- How can you ________ that he is from the North.9 -- Simply by his accent.
Whenever I go to Shanghai, _________ is quite frequent, I will visit my former teacher.