植物和动物生命活动的基本结构功能单位是（　　）

已知命题$p:\exists x\in R,2-x>e^x$，命题$q:\forall a\in R^{+},{\log }_a\left(a^2+1\right)>0$，则（   ）

下列物质属于纯净物的是（   ）

    There are two main kinds of sports. These two kinds of sports are team sports and individual(个人的) sports. Team sports are such sports as baseball，basketball and volleyball. Team sports need two separate(独立的) teams. The teams play against each other. They compete(竞争) against each other in order to get the best score. For example, in a football game, if Team A gets 7 points and Team B gets 3 points，Team A wins the game. Team sports are sometimes called competitive(竞争性的) sports.

    Besides team sports, there is another main type of sporting activity. It's individual sports. In individual sports there are no teams. People play individual sports such as swimming, skiing and running.

    Of course, it is possible(可能) to compete in individual sports. It is possible to keep a score in individual sports. The main difference, however, between team sports and individual sports is that team sports always require(要求) more than one person.