Explanation
Correct answer: B.
Choice B is the best answer. The convention being tested is punctuation between a subordinate clause and a main clause. This choice correctly uses a comma to mark the boundary between the subordinate clause (“Because...content”) and the main clause (“scientists...settlements”).
Why the other choices are wrong
Choice A
Choice A is incorrect. Joining the subordinate clause (“Because...content”) and the clause that follows (“scientists...settlements”) with the conjunction “and” results in an ungrammatical sentence that lacks a main clause.
Choice C
Choice C is incorrect because it fails to mark the boundary between the subordinate clause and the main clause with appropriate punctuation.
Choice D
Choice D is incorrect. Joining the subordinate clause (“Because...content”) and the clause that follows (“scientists...settlements”) with a comma and the conjunction “and” results in an ungrammatical sentence that lacks a main clause.