题目

听材料，回答问题。 （1） What does the speaker say about herself? A . She is very patient. B . She is in poor health. C . She is a bit independent. （2） Why did the speaker set up the organization? A . To offer those in need jobs. B . To make more profits. C . To produce masks. （3） What does the speaker mean at the end of the talk? A . She wants more volunteers. B . She has enough masks now. C . She is ready to help others.(本小题12分) 某工厂组织工人参加上岗测试，每位测试者最多有三次机会，一旦某次测试通过，便可上岗工作，不再参加以后的测试；否则就一直测试到第三次为止。设每位工人每次测试通过的概率依次为0.2，0.5，0.5，每次测试相互独立。（1)求工人甲在这次上岗测试中参加考试次数为2、3的概率分别是多少？（2)若有4位工人参加这次测试，求至少有一人不能上岗的概率。