He did n't speak as he set their drinks out , but a smirk teased at the corner of his mouth . " How did you know it was us ? " asked Sirius who , despite his best efforts at cultivating a cockney slur , still could n't manage not to sound like a proper blue - blood . " Your drinks , " Remus said as he slid into the empty seat they had left for him .

Question: What 's a possible reason Sirius bought the drinks ?
Answer: He had a smirk on his mouth .He was interested in one of the ladies that he bought the drinks for .None of the above choices .He cultivated a cockney slur .