补全对话。 上午,Dan与Joan在教室里谈话。 Dan: 1 ______, Joan! Joan: 2 ______! Sit down, 3 ______. Dan: 4 ______. Joan: 5 ______ 6 ______ 7 ______? Dan: 8 ______, thank you. 9 ______ 10 ______? Joan: I'm fine, too. Dan: Look, 11 ______this? Joan: 12 ______a football. 1.______ 2.______ 3.______ 4.______ 5.______ 6.______ 7.______ 8.______ 9.______ 10.______ 11.______ 12.______