Trees are good for human being. We can’t plant them __________ many.

A football suddenly flew over our head and it ______ missed hitting a child playing nearby.

You’d better book the tickets in advance; _______ we may miss the concert. 

Scientists have come to the conclusion_______ the temperature on Earth is getting higher and higher.

The second-hand car David bought the other day is as good as new; ______ it is in excellent condition.