Romeo doesn't want Juliet to be associated with the moon because the moon is less beautiful than the sun.
In fact, Romeo compares Juliet to the sun because she is out of his reach, very bright and beautiful, and is like the sun that guides him.
One effective method for decoding the definition of cardio respiratory, or any word, is looking at the root word. Cardio is Greek, and refers to the heart. Respiratory refers to breathing, which involves the lungs. So, cardio respiratory is the action of both the heart and the lungs.