下列各组物质，可用一种试剂加以区别的是 ①四种黑色固体：FeO、FeS、Fe、C

按要求改写下列句子。

1. I'm not sure what I can buy for my brother. ( 改为同义句)

    I'm not sure_____ _____  _____ for my brother.

2. The young man is so a strong that he can carry the heavy box.  (改为同义句)

    The young man is strong _____  _____ carry the heavy box.

3. I really don't know what I should write to him.  (改为同义句)

    I really don't know_____  _____ _____ to him.

4. What's wrong with it? (改为同义句)

    _____  _____ _____ with it?

5. We should help him to write letters. (改为否定句)

    We _____ _____ him to write letters.

节后纤维

浆砌片石的砌缝宽度不得大于（）mm。

A.40

B.30

C.20

D.10

气化炉开车吹扫时，先吹煤浆管线，后吹氧气管线。

冶炼强度提高后，中心气流发展，所以必须扩大矿批，以抑制中心气流。