2 . There's the medical bill for shots to keep the animal healthy. _________it's kept in the house 24 hours a day, a female must be given "preventive maintenance" a ten-to-twenty-dollar investment.

A．Because

B．When

C．Once

D．Unless

3 . I was having breakfast with my three children _________ water started filling my home. (用适当的词填空)

4 . I am looking forward to the day____________my daughter can read this book and know my feelings for her. (用适当的词填空)

5 . The best moment for the football star was _____________ he scored the winning goal.

A．where	B．when
C．how	D．why

6 . It’s so cold that you can’t go outside____ fully covered in thick clothes.

A．because

B．unless

C．once

D．when

7 .        a lot of hard work and a touch of luck play a part, perseverance is the key to success.

A．When

B．While

C．Because

D．If

8 . —How long will it be________ the professor makes another visit to China?
—It all depends.

A．until

B．before

C．since

D．when

9 . The firefighters were about to give up rescuing _________a weak voice came out of the ruins. (用适当的词填空)

10 . We’ll have a picnic near the river tomorrow ________it rains heavily.

A．until

B．unless

C．if

D．when