题目

Everyone needs friends. There is an old saying, Friends are God's way of taking care of us. But how do you find real friendship and keep it?    The American writer Sally Seamans tells young students some smart ways to find friends. Sally says finding friendship is just like planting a tree. You plant the seed (种子) and take care of it to make it grow.    First, you should choose a friend. What makes a good friend? It is not because a person has money or good looks. A good friend should be kind and patient. For example, if you have a bad day, a good friend should listen to your c若函数恰有三个不同的零点，则实数a的值是（   ）A．－1B．C．1或D．－1或－