Students in English-speaking countries usually address their man teacher ‘sir”, but __________ their woman teacher “madam”.

Only when the villagers were faced with water shortage___       how serious the problem of water pollution was．

So difficult ______ it to work with him in the same company that I determined to find another job.

Behind the coach ________ our team wearing blue suits.

Only when he read this novel for a second time ________ to appreciate its beauty.