单项选择题
Bob: Why didn"t you come to my party last night Bill: I"m sorry, ______ I had to visit my grandmother at the hospital.
单项选择题 Harry: I didn"t know you play billiards. Are you having fun John: I"m having a great time. ______ What are you doing
单项选择题 Customer: Could you hold the door open for a moment, please Salesman: Certainly. ______
单项选择题 【B4】
