The correct option is B After sentence (3)
Placed where it is now, sentence 2 distorts the coherent flow of ideas in the paragraph- the sentence preceding sentence 2 is describing the state of atmosphere within the passage, sentence 2 is talking about how a postmaster of a town saw the carriage pass and then the following, sentence 3, sentence reverts back to talking about the carriage. So, if we shift the placement of sentence 2 to come after sentence 3, the flow is maintained. Sentence 4, too, is connected to sentence 2 than sentence 3. This coherent flow is not achieved through any option except option C. So, option C is the answer.