问一道比较级的问题！！！

ftdonnaf

177.Bihar is India’s poorest state, with an annual per capita income of $111, lower than in the most impoverished countries of the world.
(A) lower than in
(B) lower than that of
(C) and lower than that of
(D) which is lower than in
(E) which is lower than it is in
我想问下答案B，能否用lower than that in 呢？？？？？表示lower than the income in the most ....countries，我觉得也通的呀
因为看到有的时候比较级后面补充that of/those of，但是不知道这个of为何要加上去，求指教！！！

ftdonnaf

顶顶。。。。。。。。。。。。

ftdonnaf

等牛人啊啊啊啊

VampireKiller

比较的是 annual per capital income of Bihar 和 annual per capital income of the most impoverished countries

"Bihar的人均收入" 与 "其他贫困城市的人均收入" 相比较, 并非Bihar和其他贫困城市直接进行比较.

that of 中的 that 指代 annual per capital income,    of 就是 "的" 意思.  并不能用 in 来替换.