A.cheap rockets for space travel | B.a plane |
C.a spaceship | D.a satellite |
A.in a year | B.about half a century later |
C.in the year 2050 | D.about a century later |
A.we’ll make good use of space on the earth |
B.cities under the sea |
C.Japan will first build floating cities |
D.earth’s land is in danger |
A.Travel in the Future | B.Future Life |
C.Where to Live in the Future | D.Space Travel |