题目

某主族元素R的最高正化合价与负化合价代数和为6，下列叙述正确的是 A. R一定是第VIIA族元素                       B. R的最高价氧化物为RO3 C. R的气态氢化物能燃烧                        D. R的气态氢化物易溶于水显碱性 答案：【答案】A 【解析】 【分析】 A．某主族元素R的最高正化合价与负化合价代数和为6，其最高化合价与最低化合价的绝对值之和为8，则R的最高价为+7价、最低价为-1价，为第VIIA族元素（F元素除外）； B．其最高化合价为+7价、O元素化合价为-2价，根据化合物中化合价的代数和为0确定其最高价氧化物的化Everyone needs water and a diet ___【小题1】___healthy foods. These foods should __【小题2】___some fat, some fiber, a little salt and so on. People need energy to live. They eat all kinds of foods___【小题3】__change into energy. Our bodies use different __【小题4】___of energy. The energy is measured in calories(卡路里).The more __【小题5】___we take, the more calories we burn. Even when you are _【小题6】___you are using energy ---about 65calories an hour. While you are at school, or walking home, your body is __【小题7】__up 100 calories an hour. When playing football or basketball, you might be using 400 calories an hour. On _【小题8】___Day, during the relay race, you will use most of all, perhaps as___【小题9】__as 650 calories an hour.The Chinese diet is considered to be the healthiest in the world. It contains a lot of fruit and green vegetables. It is __【小题10】___in fiber and low in sugar and fat. The Chinese eat less sugar than many___【小题11】___countries in the world. That is __【小题12】___lots of people in China have white teeth. People in the western world do no eat ___【小题13】__healthy foods. They eat too much fat and sugar and don’t take __【小题14】___exercise.Because of this, they _【小题15】___weight very easily. In order to __【小题16】___with the quick pace(步伐)of their life and work , they eat a lot of fast food . They eat a lot of sweets, soft drinks, potato crisp, chocolates, butter and ice cream and so on, ___【小题17】__are called __【小题18】__food by some epicureans (美食家).The result is that many of them become fat. In order to avoid __【小题19】___fat and __【小题20】___it is advisable (明智的)to eat a balanced diet and not eat too many foods that have a high calorie rating.【小题21】A．aboveB．OfC．atD．over【小题22】A．includeB．holdC．containD．make up【小题23】A．whichB．whatC．WhereD．it【小题24】A．numbersB．amountsC．plentyD．deal【小题25】A．exerciseB．lessonC．sport D．games【小题26】A．wakenB．runningC．workingD．asleep【小题27】A．runningB．addingC．burningD．wasting【小题28】A．ChildrenB．WorkC．SportsD．Teacher【小题29】A．muchB．manyC．fewD．little【小题30】A．poorB．lowC．richD．plenty【小题31】A．moreB．otherC．restD．others【小题32】A why         B. because  C. because of  D. since【小题33】A so          B. very     C. much       D. such 【小题34】A．a number ofB．too muchC．masses of D．enough【小题35】A．lose weightB．put onC．dieD．stay healthy【小题36】A．keep upB．carry onC．keep onD．go on【小题37】A．asB．theseC．whichD．they【小题38】A．badB．diseaseC．healthyD．junk【小题39】A．to getB．becomingC．to becomeD．get【小题40】A．keep thinB．keep fitC．stay calm D．fall ill