They did a lot of simple things to help others.
题意:根据老太太的说法,她和她的朋友在过去做了什么?
根据第一段第4-5行:
An old lady told us that when they were young, she and her friends did a lot of simple things to help others.(当他们年轻的时候,她和她的朋友们做了很多简单的事情来帮助别人。)
可知,老太太和她的朋友在年轻时做了很多简单的事情来帮助别人。
故填:They did a lot of simple things to help others.