写出同义句：This volunteer work takes thern several hours a week.

they spent several hours a week on this volunteer work
再问： They volunteer several hours a week to this volunteer work 。这样可以吗?
再答： 好牵强的，虽然没有语法错误。但是就这个问题本身是要你变词组的一些用法的。花费时间 they spend several hours a week on this volunteer work 。