new safety system _______ to use, the accident would never have happened.

What’smatterwith you —I have a cold. I want to go tobedearly.

Are you satisfied with the air today –Not at all, it’s so foggy that I often get a cough. I think we all need much ________air to breathe.

He once observed that “All happy families ________ one another, but each unhappy family is unhappy in its own way”．(2012·桂林十八校联考)

Can you walk ______ faster —- Sorry, I can’t. I am too tired ______ any more.