A butterfly valve consists basically of a disc pivoted across the bore of a ring body having the same radial dimensions as the pipe in which it is fitted.According to the above sentence, which of the following statements is not true?（）

A. The diameter of a disc is the same as the outer diameter of the pipe
B. We can infer that the valve is opened or closed by rotating the spindle
C. A butterfly valve comprises a disc and a ring body
D. The profile of the butterfly valve is a ring body