In solid geometry: the solid line is used for the visible and the dotted line is used for the invisible. It is said in the question that CB should be connected, but the picture is not good. To complete this problem, you need to connect AB and see if you can see this line to judge whether it is true or not.

In analytic geometry, solid lines are used for known lines and dashed lines are used for auxiliary lines. If the connection CB is mentioned in the title, but not in the picture, then this sentence should be drawn with a solid line under known conditions. To complete this problem, you need to connect AB. This sentence belongs to the auxiliary line in the process of proving (solving problems), and you should use the dotted line at this time.