People cut down too many trees, _____ the greenhouse effect becomes more and more serious.

I didn’t know he came back __________ I met him in the street . 

Hurry up, Jack. We have to get to the station before 11:45         we can catch the 12:00 train.

_______ she is ill, _______ she goes to school.

 --- Look, what a heavy rain! What shall we do now? --- ____________ it’s raining hard, let’s stay at home to surf on the Internet.