—I'm sorry for being late.I should have phoned you earlier.—________.I've just arrived.
This is the very plan for our May Day holiday _______ was made by our classmates.
Is _____ necessary to take off our shoes when we enter the computer lab?
____ matters most in learning English is enough practice.
Only when in the afternoon able to leave.
There are 51 students in Class Three, _____ failed in the test.