题目

完型填空。阅读短文，掌握大意，从所给的A、B、C三个选项中选出一个最佳选项。 A door was locked. A big stone came and hit the door. But he couldn’t   1    it. Later a key came. He   2   the lock and the door opened. The stone was very   3   that the key could open it so easily. He asked the key,“  4   did you do that?” The key   5   him and said, “Because I understand its 6   .” Life is just like this.   7   we want to solve a problem, we must understand it   8   . If we want to make friends with people, we must un已知点P（3，-1）关于y轴的对称点Q的坐标是（a+b，1-b），则ab的值为 ．