GMAT Sentence Correction (SC) | Re: Laos has a land area about the same as Great Britain but

This is the way I looked at it:

Laos has a land area about the same as Great Britain but only four million in population, where many are members of hill tribes ensconced in the virtually inaccessible mountain vallyes of the north.
A) about the same as Great Britain but only four million in population, where many(should refer to people, so cannot use where)
B) of about the same size as Great Britain is, but in Laos there is a population of only four million, and many (repeats the original error - 'and many are members' cannot refer to the population)
...

---