Explanation
Correct answer: D.
Choice D is the best answer. The convention being tested is punctuation use between sentences. In this choice, the period is used correctly to mark the boundary between one sentence ("In…Panchali") and another ("A quiet…time"). The phrase beginning with "a quiet" modifies the subject of the next sentence, "Ray’s film."
Why the other choices are wrong
Choice A
Choice A is incorrect because it results in a run-on sentence. The sentences are fused without punctuation and/or a conjunction.
Choice B
Choice B is incorrect because it results in a comma splice. A comma can’t be used in this way to mark the boundary between sentences.
Choice C
Choice C is incorrect because it results in a comma splice. A comma can’t be used in this way to mark the boundary between sentences.