Complex sentence: To Ransom, Oyarsa offers him the option of staying on Malacandra, but Ransom decides he does not belong there, perhaps because he feels himself unworthy and perhaps because he yearns to be back among the human beings of Earth.
Split into simpler sentences: To Ransom, Oyarsa offers him the option of staying on Malacandra. He decides he does not belong there, perhaps because he feels himself unworthy and perhaps because he yearns to be back among the human beings of earth.