题目

                     What parents owe their children?      I take the firm position that parents do not owe their children a college education.  If they can afford it ,they can certainly send them to the best universities. But they must not feel guilty if they can't If the children really want to go, they'll find a way. There are plenty of loans and scholarships for the bright and eager ones who can't afford to pay.     When children grow up and want to get married their parents do not owe them a down payment on a house. They do not have the duty to baby-sit下列说法中正确的是 [     ]A．布朗运动就是分子的无规则运动 B．多晶体的物理性质表现为各向异性C．只要外界对气体做了功，气体的内能就一定发生变化 D．物质由液态变为气态的过程，分子势能增大