各位老师好。
①Because natural gas is composed mostly of methane, a simple hydrocarbon, vehicles powered by natural gas emit less of certain pollutants than those burning gasoline or diesel fuel.
②Bihar is Indias poorest state, with an annual per capita income of $111, lower than that of in the most impoverished countries of the world.
请问老师，①这两句的of的使用方法是否一样？②of干什么成分呢？③不加of我能了解，感觉是通顺了，加了of倒是不动了。加与不加的不同之处呢？
句子来源：GMAT
①Because natural gas is composed mostly of methane, a simple hydrocarbon, vehicles powered by natural gas emit less of certain pollutants than those burning gasoline or diesel fuel.
网友需要注意of后接的是复数名词pollutants。假如没of, 则less作为限定词修饰复数名词就是语法错误了。所以这里用不定代词little的比较级less作宾语，of certant pollutants作定语。这里还应该注意：less并非表示污染物的类型少了，而是每一种污染物的排放量少了。每一种污染物都是物质名词，不可数定义，所以每一种污染物的量都少了要用less 而不是用fewer。
②Bihar is Indias poorest state, with an annual per capita income of $111, lower than that of in the most impoverished countries of the world.
这个句子中of后接in，明显是错误，不应该有任何犹豫。你此时应该核对原出处。我在百度查到的是如此的选择题：
Bihar is Indias poorest state, with an annual per capita income of $111, 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
答案选B， lower than that of. 这其实是一个非常简单的问题！
