用in return for/in turn完成句子。
1. I invited him____his kindness.为
  了报答他的好心,我宴请了他.
2.mShe gave us food and clothing and asked for nothing .
     她给了我们食物和衣服,没有要求任何回报.
3. Theory is based on practice and____serves practice.
     理论以实践为基础,反过来又为实践服务.