单项选择题
A．Because people might have to migrate there someday. B．Because it is very much like the earth. C．Because it is easier to explore than other planets. D．Because its atmosphere is different from that of the earth.
A．They eat huge amounts of food. B．They usually eat twice a day. C．They usually eat to their hearts’ content. D．They eat much less than people assume.
A．A new shuttle bus. B．A scheduled space flight. C．An airplane flight. D．The first space flight.