完形填空,We all lived on the earth.The earth (t 1) round once a

完形填空,
We all lived on the earth.The earth (t 1) round once a (d 2).As it turns,some people see sunrise and (d 3) comes to their houses; at the same (t 4) some people see (s 5) and night comes to their houses.The earth (m 6) in another way.It (t 7) round the sun in an orbit towards the(s 7).It is summer on that part of the earth.(H 8) a year later,the earth goes round to the (o 9) side of its orbit.That part of earth is now (f 10) away from the sun and has its (w 11),and the other part (h 12) its summer.Between summer and winter,(b 13) halves of the earth are the same distance (f 14) the sun.Then they have (s.15) and autumn.As the earth goes round (i 16) its orbit,we have our four (s 17) go on and on.