某些食品包装袋内有一包物质，用来吸收氧气和水分，以防止食品腐败，常称“双吸剂”．下列物质属于“双吸剂”的是（　　）

阅读下面短文，根据文章大意用所给单词的适当形式填空（未提供单词的，限填一词），使文章意思完整、正确，并将答案写在答题卡相应位罝.     

    A dog entered a butcher's shop with a note in his mouth. The note read, "$10 of lamb chops （羊排）, please. "

    The butcher was very ____ （surprise）. He took the money, put a bag of chops in the ____ （dog） mouth, and then he closed the shop ____ （quick）. He followed the dog and watched him wait for a green light. Then the dog crossed the road to a bus stop. He checked the timetable and sat on the bench. When a bus arrived，the dog checked the number and got ____ it.

    As the bus traveled out into the countryside, the dog enjoyed the scenery. After ____ while, he stood on his back paws ____ （push） the "stop" button. Then the butcher followed ____ （he） off.

    The dog ran up to a house and dropped his bag on the ground. He went back down the path, took a big run, and ____ （throw） himself against the door. No answer. He repeated the action a few times. Then a big man opened the door ____ started complaining about the dog and beating him.

    Seeing this, the butcher ran up and shouted at the man, "What are you doing? This dog is a genius!" The man replied, "Genius? No way! He has forgotten his key for the ____ （four） time this month!"

大气中有两种氧元素组成的单质，即氧气和臭氧（O₃）．在一定条件下，部分氧气转化为臭氧，下列说法正确的是（　　）