题目

两人同时向一敌机射击,甲的命中率为,乙的命中率为,则两人中恰有一人击中敌机的概率是…(    )A.              B.               C.             D. 答案：解析:甲、乙击中敌机分别记作事件A、B,则P=P(A+B)=P(A)+P(B)=P(A)P()+P()P(B)=×(1)+(1)×=.答案:A短文填空  Mental health is about the way you think and feel and your ability to deal with ups and downs. Even though you are mentally healthy, it hardly m  1   that you don’t have a mental health problem. Mental health is everyone’s b  2  . We all have times when we feel down or stressed. Most of the time those feelings pass, but sometimes they d  3   into a more serious problem. It seems that our mental health doesn’t always stay the same. It can change as the environment changes and as you move t  4   different stages(阶段) of your life. Here are four practical ways to look after your mental health. M  5   simple changes to how you live doesn’t cost much or take up lots of time. Anyone can f  6   them. ●Talk about your feelings. It can help you stay in good mental health. It isn’t a sign of      weakness, but p  7   of your ability to do what you can to stay healthy. ●Eat well. What you eat and how you feel are c  8   connected. A proper diet can have a good effect on your mental health. ●Keep in touch. Friends and family members can offer various s  9   which may help you keep active and solve practical problems. ●Take a break. It could be a weekend exploring(探测，考察) new places to enjoy the nature, or even a ten-minute break from doing your homework. A few minutes can be e  10  to relax you.