酶对底物的Km值越小，则它对底物的（）越大。

When I was twelve years old, my family were the first black people to move into an all white part of Grand Rapids, Michigan. Many of our new neighbors weren’t very welcoming. Some of them said angrily that we should return to where we came from. The children sometimes threw stones at me .

Most of my teachers simply took no notice of me, but not Dorothy Bean, my history teacher. Miss Bean was angry at how badly I was being treated, but she didn’t say this to me. Miss Bean showed her respect for me by teaching me just like anyone else. Instead of being unnoticed, I was given a chance to show that I was clever. Miss Bean was the first teacher who ever made me think for myself. She always wanted to know what I thought about different questions. She expected me to have my own idea. Miss Bean was teaching me that thinking for oneself was the real key to education.

One day, when I was not paying attention in class, Miss Bean suddenly threw an eraser(黑板擦) at me. The eraser hit me right on the hand and sent my pencil flying. The whole class were very surprised at first, then started laughing. This event became famous in the school and, because it happened to me, the students wanted to get to know me. So that’s the story of how Dorothy Bean made me her target(靶子). However, what I want to do is express my thanks to her.

56. The author and his family were not welcomed by the local people because ____________.

A. they returned from another country     B. they have different skin color

C. they spoke a different language         D. they moved to a wrong place

57. From the end of the first paragraph we know that _____________.

A. children were more friendly to strangers

B. American schools were not safe for kids

C. children often follow their parents’ behavior

D. fighting each other is part of children’s nature

58. Miss Bean respected the author by ____________.

A. giving him special attention.

B. hitting him with an eraser.

C. giving him extra lessons.

D. treating him as one of her students.

59. To Miss Bean the most important thing for a student is to _________.

A. pay close attention to what the teacher says.

B. learn to think and have one’s own idea.

C. keep silent and unnoticed in class.

D. get special attention from the teacher.

60. Which is the writer’s attitude to Miss Bean?

A. Grateful.      B. Hateful.      C. Negative.       D. Supportive.

危险源产生的根源来自哪三个方面？

解决我国流动性过剩问题的政策建议

用于判别具有表面粗糙度特征的一段基准线长度称为（）。

A.基准线

B.评定长度

C.取样长度

D.轮廓的最小二乘中线

目前船体构件边缘加工的主要工艺方法是（）。

A、机械剪切

B、气割

C、刨边

D、铣边