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【简答题】
在机器人兴趣班,男生有24人,比女生人数的2倍还多4人。女生有多少人? ( )人数×2+4人=( )人数 解:设女生有x人 方程:( )
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皮皮学刷刷变学霸
举一反三
【单选题】在一个关系中要找出满足指定条件的元组组成新关系,应使用的操作是( )。
A.
专门的关系运算包括投影、选择和联接。选择运算是从关系中找出满足给定条件的那些元组,这种运算是从水平方向抽取元组;投影运算是从关系模式中挑选若干属性组成新的关系,这是从列的角度进行的运算,相当于对关系进行垂直分解;连接运算是将两个关系拼接成一个新的关系,生成的新关系中包含满足条件的元组。在一个关系中要找出满足指定条件的元组组成新关系属于选择运算。
B.
选择运算
C.
查询运算
D.
投影运算
【单选题】普萘洛尔治疗心绞痛的主要药理作用是
A.
阻断心脏β1受体，降低心肌细胞耗氧量
B.
加强心肌收缩力，加强心脏泵血功能
C.
扩张冠脉
D.
降血压，减低心脏前负荷
E.
降低左室壁张力
【简答题】“We started as a group of friends with the same problem: difficulty in our personal life to manage our time, being always in a hurry.” This thought was recently offered by Bruno to explain the origin ...
【单选题】His excuse for being late this morning was his car had ______ in the snow.
A.
started up
B.
got stuck
C.
set back
D.
stood by
【单选题】His father, a famous university professor, who is said to have started his teaching career in Australia, _____ in Nanjing University for more than twenty years.
A.
has worked
B.
worked
C.
is working
D.
will work
【简答题】A small group of people around the world have started implanting(移植) microchips to link the body and the computer. Mr. Donelson and three friends, who had driven 100 miles from their homes in Loekport...
【简答题】He started his career working for a television station.
【单选题】Mr. Li swimming for 3 hours, and his son an hour ago. [ ]
A.
has been; started
B.
have started; has started
C.
started; started
D.
has started; has started
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