While _______ across the street, you should be careful.[ ]

We usually schoolat 7:30 in the morning and homeafter school at 4:30 in the afternoon.

______, how long does it take you to fly to Xi’an from Nanjing — About 2 hours.

It’s snowing heavily outside. Put on your coat,_________ ,you’ll catch a cold.

we have done a lot to build a low-carbon economy,yet it is still _________ ideal. We have to work even harder.