单项选择题

将一枚硬币独立地掷两次，引进事件：A 1 ={掷第一次出现正面}，A 2 ={掷第二次出现正面}，A 3 ={正、反面各出现一次}，A 4 ={正面出现两次}，则事件

A．A 1 ，A 2 ，A 3 相互独立
B．A 2 ，A 3 ，A 4 相互独立
C．A 1 ，A 2 ，A 3 两两独立
D．A 2 ，A 3 ，A 1 两两独立
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单项选择题
What s the main idea of the passage
A．Parents have more influential power on children"s achievement than teachers.
B．It"s sad to see so many parents not making the most of their children"s intelligence.
C．Teachers and educators ask parents not to educate their children before school.
D．Parents are afraid to teach their children at home.
单项选择题
What did the doctor do
A．lie had an accident.
B．He revealed the truth.
C．He was not in good condition.
D．He was conditionally responsive.
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