天文学家发现了许多可能适合人类居住的星球。

Astronomers have discovered many potentially habitable ___worlds.

科幻小说经常描绘外星世界与地球截然不同的景象。

Science fiction often portrays alien ___worlds with landscapes vastly different from Earth.

兄妹俩的性格截然不同。

The brother and sister are ___worlds apart in personality.