某位同学抛掷两枚硬币，抛出两个正面朝上的可能性为______．

搜题请搜索小程序“爱下问搜题”

问题解答题

答案

根据题意得：

抛掷两枚硬币可能出现的情况有：正正，正反，反正，反反；

所以恰好两个正面朝上的概率是

．

故答案为：

．

单项选择题

Control valves of a CO₂ system may be located within the protected space when（）.

A.it is impractical to locate them outside

B.there is also a control valve outside

C.the CO₂ cylinders are also in the space

D.an automatic heat-sensing trip is installed

单项选择题

双工器的垂直极化用符号（）表示.

A.H

B.I

C.V

D.E