填空题
[听力原文]11-15
On Thursday afternoon Mrs. Clark got dressed for going out. She took her handbag, with her money and keys inside it and left her house, pulling the door behind her to lock it. At six o’clock she came home and got into the house with her key. At once she smelled cigarette smoke. Cigarette smoke in her house How Had anybody broken in while she was at the club She checked the back doors and all the downstairs windows. They were all securely fastened. There was no sign that anyone had forced his way in. But one thing was certain: a cigarette had been smoked in her house that afternoon.