Later in this chapter cases will be introduced to readers ______ consumer complaints have resulted in changes in the law.（2008江西卷）

where

主干句子，cases will be introduced to readers 

case 是主语，will be introduced 是谓语，to readers 对象，状语，later in this chapter 地点状语

后面是一个定语从句，意思是：消费者投诉导致了法律的新变化，是读者还是案例为本定语从句的先行词，现在能判断出应该是case为先行词

将cases放到从句中，consumer complaints have resulted in changes in the law 主语、谓语、宾语都不缺，缺的是状语，in the cases，在那些案例中，因此用where指代，选A

case 做先行词，它的从句总是用where 引导。如：
1.  There are some cases where the rule does not hold good. 
在有一些案例中，规则是无效的。
2.  There are many cases where the pen is mightier than the sword. 
文胜於武的情形很多。
3.  The legal precedent applies to cases where the parents of the child are divorced。 
该法律先例适用于已离婚的孩子的双亲的诉讼案。