题目

If you want to see a thing well, reach out and touch it! That may seem a strange thing to say. But touching things can help you to see them better. Your eyes can tell you that a glass ball is round. But by holding it in your hands, you can feel how smooth and cool the ball is. You can feel how heavy the glass is. When you feel all these about the ball, you really see it. With your skin, you can feel better. For example, your fingers can tell the difference between two coins in your pocket. You can feel a little drop of water on the back of your hand, too. You can even feel sounds ag19．“春江潮水连海平，海上明月共潮生．”关于潮汐现象的形成原因，下列说法正确的是（　　）A．潮汐现象是由于地球和太阳对月球引力共同作用的结果B．潮汐现象只是由于月球对地球上的海水引力作用的结果C．潮汐现象只是由于太阳对地球上的海水引力作用的结果D．潮汐现象是由于太阳对地球上的海水引力和月球对地球上的海水引力共同作用的结果