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【单选题】
设关系 R 与关系 S 具有相同的目数(或称度数),且相对应属性的值取自同一个域,则 R - (R - S )等于 _________ 。A.
R∪S
B.
S
C.
S - R
D.
R∩S
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【单选题】According to Paragraphs 5 and 6, which of the following is INCORRECT?
A.
The gold rushes brought about more opportunities for crimes.
B.
Banks gained their prosperity in frontier towns after 1849.
C.
After the Civil War, thieves turned to steal cattle and horses.
D.
In Texas, cattlemen had to fight for the access to land and water.
【简答题】下述循环体语句的循环次数为()。
int x=-1;
do
{ x=x*x; } while(!x);A. 1次 B. 2次 C. 无限次 D. 有语法错误
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【简答题】The following questions refer to information given in paragraphs 1–6. Match them with each paragraph and then answer the following questions.
【简答题】读下面地理景观模式示意图，AB 表示昏线，H1 和H2 分别代表当地对流层的高度，此时南极圈以内全部出现极昼现象，回答后面问题。 （1）此时 a 角的度数 。北京时间是 。 （2）A、B两地对流层H1和H2厚薄关系是 。 （3）海洋C处此时气压中心的性质是 ，简述其成因 、 。 （4）D处气候特点是 。 （5）M应属于地球圈层中的
【单选题】According to paragraphs 5 and 6, one disadvantage very young children face in processing information is that they cannot
A.
process a lot of information at one time
B.
organize experiences according to type
C.
block out interruptions
D.
interpret the tone of adult language
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