【正确答案】 B

【答案解析】[解析] 题目是“他们为什么一晚上都在担心”。此题可以在短文第五段最后一句中找到答案。“because they were worrying all the time about finding the person who had sent them the tickets．”意思是“他们一直想找到到底谁给他们送的票”所以答案为[B]。