OG 11 100 需要解释

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    (correct)

  C    
and lower than that of

  D    
which is lower than in

it有明确的指代对象。文中的两个比较对象是“an annual per capita income of $111”和“the most impoverished countries of the world的income水平”。所以it出现即可以指代111，又可以指代“the most impoverished countries of the world的income水平”，有歧义。

1，比较考点的代词都用that或those

2，b这个选项简洁