The correct option is E comparable to that of Great Britain but a population of only four million people, many of whom
The sentence has a parallel structure that compares the land area and population aspect of Laos and Great Britain. It has three major errors. First, it compares the land area of Laos with Great Britain - this is inappropriate. The more apt comparison would be with the land area of Britain. Secondly, use of 'four million in population' is non-idiomatic and the correct idiom would be more parallel to 'a land area'. Finally, in the given context 'where' must refer to a place and not to 'population' as it wrongly does in the sentence. Option A is out due to these reasons. Option B too has the first error mentioned - comparison of land area with Britain. Also, because 'many are members...' is presented as an independent clause, it is unclear who the 'many' refers to. Additionally, '....but in Laos there is a...' seems superfluous. The contrast presented in this option - between Laos having land area comparable to Great Britain's and many of its population being members of hill tribes is illogical. This is not what the sentence means to say. Also, it is not clear what 'them' is referring to. D repeats the original errors of the sentence. E is the correct answer with logical comparison, correct idiom and parallelism.