for(;;)是什么结构？
A、循环结构
B、分支结构
C、顺序结构
D、调用结构

单项选择题In a female human cell, what would be the effect on X inactivation if a mutation occurred in the Xist gene making it nonfunctional? A、One of the two X chromosomes would become inactivated. B、Both of the X chromosomes would become inactivated. C、Neither of the X chromosomes would become inactivated. D、Only the maternal X chromosome would become inactivated. E、Only the paternal X chromosome would become inactivated.

单项选择题计算机系统中的内存储器容量一般比外存储器的容量小。 A、正确 B、错误