— Hurry up. The bus is coming.— Oh, no. We mustn’t cross the street ________ the traffic light is green.
Tom and Mary _______ to China last month.
--- What’s the use of this kind of fuel(燃料) ? --- It can make the train __________ fast.
---Help yourself to some chicken , Jim . ---__________________
In our class, Andy is the __________ . He always makes everybody laugh .
---The classroom is not________ clean ______it was yesterday . ---Sorry, I forgot to clean it.