请问此句子中to restore...不定式短语的逻辑主语应该是them (waves) 或是force (the gr

请问此句子中to restore...不定式短语的逻辑主语应该是them (waves) 或是force (the gravity of the earthOnce ocean waves have been generated,the gravity of the earth is the force that them in a continual attempt to restore the ocea surface flat plane.对不起掉了一个词drive.和to a 正确句子是：Once ocean waves have been generated,the gravity of the earth is the force that drives them in a continual attempt to restore the ocea surface to a flat plane.