This is Lily. She's a girl.

命题若“x²+y²=0，则x=y=0”的否命题是（　　）

A: Good afternoon! How are you?

B: Fine, thank you. Oh, that's Tom speaking.

A: You're right.____

B: Sure,but she is doing her homework. Wait a moment. Lucy, it's Tom.

(After Lucy answers the phone. )

C: Hello. Tom.

A: Hello, Lucy.____

C: I have no idea. How about you?

A: I'm going fishing nearby on Saturday. Would you like to go with me?

C: ____ I'm sure we can have fun together. By the way, How can we get there?

A: ____ It's not far from here.

B: Sounds good. ____

A: Let's make it 8 :00 am at the school gate. OK?

B: OK. See you then.

A: See you.

【提出问题】这块黄色的金属是黄金还是铜锌合金?

【猜想】①小新认为是黄金；②小宝认为是铜锌合金。

【查阅资料】合金中的金属保持各自的化学性质，金在高温下不与氧气反应，锌在高温下与氧气反应生成白色固体。

【设计实验】

①小新设计的实验是截取一小片黄色的金属放在石棉网上用酒精灯加热；

②小宝设计的实验是截取一小片黄色的金属放入硝酸银溶液中。