Later in this chapter cases will be introduced to readers __

where
搞清楚句子成分先
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

选择A 是因为，本句是含有定语从句的复合句。其中，
______ consumer complaints have resulted in changes in the law.是定语从句
从句中主语是consumer complaints；谓语是have resulted in ，宾语是changes in the law
主谓宾齐全，只能选副词作状语了。
翻译句...