Some aspects of a pilot's job      be boring, and pilots often      work at inconvenient hours．

My newly- purchased bag is nowhere to be found.____ I have left it on the bus?

I got close enough to hear them speaking Chinese, and I said “Ni Hao ” just as I ____ do in China.

According to the traffic rules, you _________ wear the safe belt while you are driving.

Delta, the American airline, is sometimes jokingly explained “Don’t expect your luggage to arrive” because it ______ be very slow.