Now we all know that there are nine planets in solar (太阳的) system.

问题补充：

Now we all know that there are nine planets in solar (太阳的) system.

答案：

解析：本题考查形容词。Solar system为“太阳系”之意，注意不可写成名词形式。句意：现在我们都知道在太阳系内有九大行星。