求助一道OG语法题

hollyyao

Laos gas a land area about the same as Great Britain but only 4 million in population, where many are members of hill tribes ensconced in the virtually in accessible mountain valleys of the north.
B. of about the same size as Great Bratain is, but in Laos there is a population of only 4 million, and many     这里Laos land area 和Great Bratain的大小比，为什么说他是和Great Bratain 比
C. that is about the same size as Great Bratain's land area ,but in Laos whith a population of only 4 million people, many of them  这里为什么不能用them, 而是whom，还是不太懂
谢谢！

HarrisZheng

问题1  B选项的意思就是和GB比   如果要用这样的写法 要改成 as GB has

问题2 many of whom是定语从句  many of them的话 前面要改成分号，或者加连词。