题目

二．完形填空： Why did I come today? I wondered. My Christmas   16   contained several people that claimed they wanted nothing but I knew their feelings would be hurt   17   I didn’t buy them anything, so gift buying was   18   but fun. Hurriedly, I finished shopping and   19   the long checkout lines. In front of me were a boy of about 5 and a younger girl. She carried a beautiful pair of    20   slippers. When we finally   21   the checkout register, the girl   22   placed the shoes on the counter. She treated them as though they were a   23  .  “T有①空气；②氧气；③铜；④氯酸钾；⑤氧化镁；⑥冰水混合物六种物质中，属于单质的有______；属于氧化物的有______；属于化合物的有______；属于混合物的有______（填序号）．