题目

阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。 We think that life in Chinese high school is a hard experience in which we have to survive mountains of homework and all kinds of exams. Yet would it be(surprise) if I tell you that high school life in the US is almost as hard it is in China? In US high school, everything must (record) into your studying document(文件), including your grades, tests and final examinations. Failing (turn) in your homework on time will directly affect your grade for a certain course. Perhaps completely di 乒乓球比赛规则规定：一局比赛，双方比分在10平前，一方连续发球2次后，对方再连续发球2次，依次轮换，每次发球，胜方得1分，负方得0分．设在甲、乙的比赛中，每次发球，发球方得1分的概率为0.6，各次发球的胜负结果相互独立，甲、乙的一局比赛中，甲先发球． (1)求开始第4次发球时，甲、乙的比分为1比2的概率； (2)ξ表示开始第4次发球时乙的得分，求ξ的期望．