玉和宝的主要区别?
参考答案:
玉性主温,宝石性主寒;玉四季皆宜,宝石宜于夏,
玉之美德,温润而泽,能和人之心性,养人之心性;宝石多浮光能悦人之目,不能悦人之心。
According to the passage, why do people join groups that practice secondary cooperation
A.To share the happiness with others.
B.To get rewards for themselves.
C.To associate with people who have similar backgrounds.
D.To defeat a common enemy.
X、Y、Z和R为原子序数依次递增的四种元素。其中X、Y同周期,X的最高正价是最低负价绝对值的3倍,Y、Z、R同主族,R为人体所需的微量元素。下列说法不正确的是 [ ]
A.127R-的核外含有54个电子
B.Y、Z、R的氢化物对应酸得酸性逐渐增强
C.有l molY的单质与水发生反应则转移电子的物质的量为2 mol
D.在含有Z单质的水溶液中,通入足量XO2气体,则溶液由黄色变为无色