(2013·新课标全国卷Ⅱ)A serious study of physics is impossible ________ some knowledge of mathematics

My son is addicted to drugsHe isn’t hopeless, is he?— Yes, ______ he mends his way and starts all over

ctory produces half amillion pairs of shoes every year, _________ are sold abroad

long time ______ I last saw you.—Yes, and it will be another month ______we can meet again.

We have to give the users something new ________ what we’ve already offered, which is the only way to broaden the appeal of the website.[ ]