题目选项分析

A study of kindergarten students has shown that children from households that own many books, an average of 54 books, show average or high reading achievement levels, while the households of children with lower reading achievement levels tend to own fewer books, 5 books on average.

What additional information would strengthen the assertion that parents who don't buy children's books to keep in the home cause their children to fall behind their peers in reading skills?

【选项】The children in the study all had unlimited access to thousands of elementary school library books.