CORRECT answer is option 4) i.e. BADC.Sentence 'B' is the only independent sentence, hence, it will be the FIRST sentence.Sentence 'A' will follow the sentence 'B' because sentence 'B' talks about GREYHOUND sport and sentence 'A' talks about the Greyhounds when their CAREER is over. This combination i.e. BA is given in only one option i.e. 4. Hence, the correct answer is option 4.