Answer:
(B) area; the size of the population, however, will
Explanation:
In option A, a comma was used to join two independent clauses. That is inappropriate. In option C, there should be a semicolon before the word 'however'. In option D, the modifier 'the number' is not appropriate. In option E, the word 'when' is not needed. Therefore, only option B is correct. The use of a semicolon is appropriate.