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【单选题】
乳糖操纵子是A.
由一组结构基因组成
B.
由结构基因和调节基因组成
C.
由操纵基因和启动基因组成
D.
由结构基因、操纵基因和调节基因组成
E.
由启动基因、操纵基因、结构基因和调节基因组成
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举一反三
【简答题】Now a paper in Science argues that organic chemicals in the rock come mostly from ________ on earth rather than bacteria on Mars. A) configuration B) constitution C) condemnation D) contamination
【单选题】关于NSString类型的描述中,哪一项是错误的?
A.
NSString 是Objective-C中的类
B.
NSString 类型的常量，必须用双引号引起来，并加@字符，如：@”hello”
C.
NSString 类型与C语言的字符串类型之间可以相互转换
D.
使用NSLog输出字符串，用%s作为输出变量的格式符
【简答题】阅读理解 Take any long piece of paper. Now glue the ends of the paper together. You have made a ring. Take a second long piece of paper. Twist the paper once and glue the ends together. Now you have made ...
【简答题】阅读下列代码 - (NSString *)description { return [NSString stringWithFormat:@"%@", self];}下列关于程序执行结果的描述中，正确的是（）。A. 无输出结果 B. 程序陷入死循环 C. 循环引用 D. .无错误
【简答题】autoreleasepool{NSString *per = [[NSString alloc] init];[per retain]; [per retain]; per = @”aa”; [per release];[per release];[per release];}
【单选题】Now a paper in Science argues that organic chemicals in the rock come mostly from ________ on earth rather than bacteria on Mars.
A.
configuration
B.
constitution
C.
condemnation
D.
contamination
【单选题】______ over 100 years since the invention of the square-bottomed paper bag.
A.
Now is
B.
Now it has
C.
There is now
D.
It is now
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