I was caught in the traffic jam this morning; ______, I would have come on time.
Is _____ necessary to take off our shoes when we enter the computer lab?
____ matters most in learning English is enough practice.
Only whenin the afternoonable to leave.
There are 51 students in Class Three, _____ failed in the test.
______ happened to be no one in that house when the typhoon hit the area.