头道麦汁过滤时，要尽量沥干，至麦糟出现裂缝再放洗糟水，这样有利于洗糟。

“x＞1”是“x≥1”的（　　）

A．充分而不必要条件

B．必要而不充分条件

C．充分必要条件

D．既不充分也不必要条件

(3分)如图5所示电路，导线a的一端固定连接在铅笔芯上，当导线b的一端在铅笔芯上左右移动时，灯泡亮暗会发生变化这个实验说明铅笔芯是__________（选填“导体”或“绝缘体”），还能说明导体的电阻与_________有关，受此启发，人们制造了一种可以改变电阻的元件，叫做________________.

用恰当的词语填空，完成对话。每空一词。

A: Hi! Linda!

B: Hi! Michael!

A: What bad 1_______! There is so much sand and dirt in the air.

B: So it is. Have you 2_______ of the sandstorm?

A: No, I haven't. What's that?

B: There is lots of sand flying in the air when the wind is 3_______ strongly.

    So we can't see anything clearly outside.

A: But what 4_______ these sandstorms?

B: People do something harmful to destroy the environment, such as cutting down too many trees.

A: That's too bad. I think we still need to work hard to 5_______ our environment.

B: Yes, I agree with you.

取一定量的CuO粉末与0.5L稀硫酸充分反应后，将一根50g铁棒插入上述溶液中，至铁棒质量不再变化时，铁棒增重0.24g. 并收集到224mL气体（标准状况）。求此CuO粉末的质量。

我国果品储藏量仅占当年水果总产量的5%左右。