The Earth is one of the known planets that circle the sun. In -----6----- times, the men who studied the ----- 7----- noticed that while certain heavenly -----8----- seemed fixed in the sky, others seemed to -----9----- about. The latter they named planets or wanderers -----10----- astronomers have discovered that the four planets, Jupiter, Saturn. Uranus -----11----- Neptune, are surrounded by poisonous gases and are so ----12------ that any living thing attempting to ----13------ on them would instantly be frozen to death. Of the five remaining -----14----- Venus most closely ----15------ the Earth in size.
Choose the best word in the given passage.