the city’s public school system should be open to the children of migrant workers has bec

问题补充：

the city’s public school system should be open to the children of migrant workers has become the focus of discussion.

A. That

B. What

C. Whether

D. If

答案：

A. That

B. What

(答案→)C. Whether

D. If

解析：考查主语从句。本句中的Whether the city’s public school system should be open to the children of migrant workers是一个主语从句，因为主语从句中的句子结构很完整，使用不能使用what，因为what在句中要做主语，宾语，表语等。If不能引导主语从句，that表示的是确定的事情。句意：公立学校是否要对移民的工人开放这个问题已经成为了讨论的焦点。故C正确。