This activity can not only boradens our horizon but also foster our noble spirits .
问题描述：
This activity can not only boradens our horizon but also foster our noble spirits .
I guarantee that you will enjoy yourself.请问foster是否要加s
答
不用,foster前面省略了情态动词can
另外boradens打错兼用错,应该是broaden,情态动词can后面的动词不用单复数变化