As soon as his teacher begins lecturing, he begins to doze off, not intentionally but _______.

She is fed up with sharing a house with others; ___, she is looking for her own flat. 

The rapidly growing birth rate brings about a lot of environment problems, which the government is supposed to take _____.

I must go now. _____, if you want that book I'll bring it next time.

The player kept on running ___ it was raining heavily.