As nobody here knows what is wrong with the machine, we          send for an engineer to handle the problem．

When the traffic lights are red, we _______ stop.

—Amazing! You       wear slippers at work．— Don’t you know it’s a fashion?

—Could I use your phone? —Yes, of course you ____ .

—Why are those people gathering in the middle of the street?—I don’t know. There ________ be an accident.