题目

下列各组粒子半径大小的比较中错误的是( )A. K＞Na＞Li B. Na＋＞Mg2＋＞Al3＋C. Mg2＋＞Na＋＞F－ D. Cl－＞F－＞F 答案：【答案】C【解析】核外电子排布相同的离子，核电荷数越大离子半径越小，故离子半径Mg2+＜Na+＜F-；A.同主族元素自上而下原子半径逐渐增大，故原子半径K＞Na＞Li，故A项正确；B.核外电子排布相同的离子，核电荷数越大离子半径越小，故离子半径Na+＞Mg2+＞Al3+，故B项正确；C.核外电子排布相同的离子，There is an English saying :“laughter is best medicine .”Until recently ,few people took the saying seriously .Now however ,doctors have begun to look into laughter and the effects it has on the human body .They have found that laughter really can improve people’s health .Tests were carried out to study the effects of laughter on the body .People watched funny films while doctors checked their hearts ,blood pressure ,breathing and muscles .It was found that laughter had similar effects to physical exercise .It increases blood pressure ,the heart beating and breathing ; it also works several groups of muscles in the face ,the stomach ,and even the feet .If laughter exercises the body ,it must be beneficial .Other tests have shown that laughter appears to be able to reduce the effect of pain on the body .In one experiment doctors produced pain in groups of students who listened to different radio programmes .The group that tolerated(忍耐)the pain for the longest time was the groups which listened to a funny programme .The reason why laughter can reduce pain seems to be that it helps to produce a kind of chemicals in the brain which diminish both stress and pain .As a result of these discoveries ,some doctors in the United States now hold laughter clinics ,in which they help to improve their patients’ condition by encouraging them to laugh .They have found that even if their patients do not really feel like laughing ,making them smile is enough to produce beneficial effects similar to those caused by laughter .【小题1】Doctors have proved the following EXCEPT that      .A．smiling does good to healthB．laughter can be toleratedC．there is a way to reduce painD．laughter can work the muscles in the feet【小题2】The main idea of the passage is       .A. laughter and physical exercise have similar effects on the human body B smile can produce the same effects as laughter C. pain can be reduced by laughterD. laughter is the best medicine 【小题3】The students who    tolerated the pain for the longest time .A．listened to different radio programmesB．could produce a kind of chemical C．don’t have stress of painD．listened to a funny programme【小题4】The underlined word “diminish” is similar to       .A．testB．stopC．reduceD．increase【小题5】Doctors hold laughter clinics _________. A．to give better condition to their patientsB．in order to improve patients’ health C．to make patients smileD．to prove smile and laughter have the same effect