A:42He原子核内含有4个质子
B:32He原子核内含有3个中子
C:32He和42He互为同位素
D: 42He具有较强的金属活动性
已知集合A=x,y|y-3x≤0,B=x,y|x2+(y-a)2≤1,若A∩B=B,则实数a的取值范围是( )
Of all the things we eat and drink,water is the1important.The human body can go2 food for a long time,but two3three days without water could make people4. A lot of people don't understand how5water the human body needs6well and many people don't drink enough,esecially in7weather. Most people drink8they are thirsty but in fact they need more water,expecially when they take9.A man's body is 65 to 75 percent of10. If we don't have enough water. We fell tired and may become ill.