人体中最坚硬的器官是（    ）

B

    Today is Sunday. Mike and Peter 1 go to school. Listen! They are talking about the life 2 in the room.

    "3 will the world be like" asks Peter. "I think that the world will be a 4 place to live in. And we will 5 machines and robots at home. They will help us do lots of 6." says Mike.

    "The robots will help 7 cook dinner, clean the houses and 8 the old people. I think there will 9 a kind of medicine (药) and it can make me 10 more than 100 years ," Peter says.

    "What will you do then?" asks Mike.

    "Then I will take my great – grandchildren to the moon," says Peter. "The moon? I will go to the Mars (火星) with my wife ," says Mike.

氟氧酸是较新颖的氧化剂，应用性极强，可用被氮气稀释的氟气在细冰上缓慢通过制得：F₂+H₂O=HOF+HF．该反应中水的作用与下列反应中水的作用相同的是（　　）