—It’s eight o’clock already. Jack      be here by now.—Oh, he told me that he was going to see his dentist and wouldn’t be back until ten.

 But for friction (摩擦力), people ______ neither walk, nor even stand up.

---.Don’t you think it necessary that he ____to Miami but to New York? ----I agree , but the problem is _____he has refused to.

一What does the sign over there read?一“No person ______ smoke or carry a lighted cigarette, cigar or pipe in this area.”

-- I ________ to your birthday party last Sunday!-- Unfortunately, you were on business.