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【单选题】
设N和Z分别表示自然数和整数集合,则对减法运算封闭的是 ( )A.
N
B.
{x÷2|x∈Z}
C.
{x|x∈N且x是素数}
D.
{2x+1| x∈Z }
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举一反三
【单选题】When it was my turn to introduce myself, I was so nervous that my mind went ______.
A.
blank
B.
faint
C.
vain
D.
dim'
【简答题】阅读理解。 It was my first day at school in London and I was half-excited and half-frightened. On my way to school I wondered what sort of questions the other boys would ask me and rehearsed (practiced) al...
【简答题】It was my(luck) ______ day. My bike broke down half way to school and I was late for class.
【简答题】异形柱的画法?
【简答题】It was my first day of high school, and I was late. My next class, Spanish, scared me. I just could not speak that language. As the bell rang, I ran to the classroom. At the door, a hand reached out a...
【多选题】在软件中,处理异形暗柱时,软件提供了什么方法
A.
新建异形柱、按墙位置绘制暗柱等的方法画出异形截面
B.
自适应布置柱
C.
使用快捷键SHIFT+Z
D.
提取CAD图元
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