语法题请教~

单选：

1。It is difficult for present-day readers ____ Sister Carrie was withdrawn from circulation at the turn of the century.

A. to understant the novel why

B. to understand why the novel

答案选B，为什么不是A？？？

2。___economic change by investigating the fluctuations in the relationship between workers' wages and their buying power.

A. Economists gauge how

B Economists gauge

答案选B，为什么不是A？？？

改错：

During the pre-Revolutionary period, the press in Britain's North American colonies was subject to licensing laws similar to them of Great Britain itself.

答案是说them错了，可是我觉得subject也因该改成subjected，没错么??????

谢谢各位了~！

1.the novel Sister Carrie 才是完整的从句主语.如the novel Uncle Tom`s Cabin

2.economic change 是一名词词组作句子的宾语,句子缺主谓。当然选B。

3.be subject to是固定用法.