Explanation

Creating a filter: in this question, the construction "in which" may stand out. The answer choices show that "in which" and "when" are alternatives we must choose between. Both phrases, "in which" and "when," convey meaning accurately here. More of a problem is the phrase "in then Homo Sapiens' inhabited areas," an awkward string of words.

Applying the filter: (B) looks better and clear. Choice (C) has strange phrasing that leaves us uncertain whether the two groups are in the same area, as the sentence intends to say. Choice (D) has the same problem as (A). Choice (E) distorts the meaning of the sentence; the intended meaning isn't that any areas belonged to Homo Sapiens; we're talking about cohabitation. The correct answer is (B).