脊索瘤和脑膜瘤均为先天性中枢神经系统肿瘤。

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填空题

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	a. My grandma ______ in a small house many years ago. b. My grandma ______ in a big house now.
	a. ______ is thanLing. b. Ling is ______ than Tom.
	a. Tom is ______ for Daming. b. Ling is ______ for Sam.
	a. The boy ______ football yesterday. b. The boy ______ table tennis tomorrow.

多项选择题

按用途划分为（）三类。

A.结构钢

B.工具钢

C.特殊性能钢

D.优质钢