参考答案：simple，immediate and directive

解析：[题眼] In the conversations with their child，parents tend to use ______ words because of the busy lives parents lead．
[定位] 第2个小标题Good readers have better vocabularies下第1、2句：Think about the conversations you’ve had with your child today．There’s a good chance that—because of the busy lives parents lead—most of the words you use are simple，immediate and directive．
空白处应该是形容词作定语，修饰名词words。从原文中可以看出，答案应该是simple，immediate and directive。