The new examination system has to be _______ in special regions before it can be applied nationwide.[ ]

She is a quiet girl at school，but sometimes she _____ be very naughty.

I’d like to ___________whether Flight 245 for San Francisco is departing on time .

American students take part in a wide variety ofafter-school activities _______ they develop their social skills.

Can you tell the ________ difference between thewords “require” and “request” I sometimes get puzzled by their meanings