题目内容

凡在短期内,现象有周期性规律的规律变动,都不能称为季节变动。

A. 对
B. 错

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High-speed steel is also___________________(know) as self-hardening steel.

The more carbon the steel contains and the ________________(quick) cooling is, the __________________(hard) it becomes.

High carbon steel may be ____________________(harden) by heating it to a certain temperature and then quickly cooling in water.

Heat-resistant steel is made by ________________(add) some tungsten and molybdenum.

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