While we ________ an English song, some visitors came into our classroom.
were singing
sang
are singing
He has to be ________ bed ________ nine o’clock.
I have ________ homework to do this evening.
—Dad,must we wait until the light becomes green? —Yes,I’m afraid we ________.That’s the traffic rule.
—It is rather cold here.Shall we light a fire(点火)? —No,you ________,because things here are easy to catch fire.
My sister is ________ a new song.Me,too.