2 . ______ earth is only a small planet in ______ Galaxy.

A．The; a

B．The; the

C．An; a

3 . Which is bigger, ________ sun or ________ earth?

A．a; a

B．a; the

C．the; a

D．the; the

4 . —It’s ________ exciting day, isn’t it?
—Yes, it is. Well, ________ sun is going down. We have to go home.

A．a; a

B．a; the

C．an: the

D．an; a

5 . China has set a goal of sending astronauts to ________ moon.

A．a

B．an

C．the

6 . ________ earth is much bigger than ________ moon.

A．An; a

B．An; the

C．The; the

D．The; a

7 . More and more people realize saving ________ earth begins with small things.

A．a

B．an

C．the

D．/

8 . —Everyone in the world should play ________ role in saving ________ earth.   
—I agree with you. It is our home.

A．a; the

B．a; an

C．the; a

9 . —Do you want to be __________ astronaut when you grow up?
—Of course. I also hope to take a spaceship to__________ moon in the future.

A．a; a

B．an; the

C．a; the

D．an; a