Personally, I think the best posture is: Figure C.

Regarding the dispersion of the center of gravity, it should be 25% on the handlebar, 35% on the seat, and the rest on the pedal.

If you feel that XX is pinned down, put your body back and let your P-share egg support the cushion.

Don't straighten your arms when riding, or you will be very tired. Like an O-leg, keep your elbows out and relax.

The position of the pedal should be one-third of the front foot, so that the horizontal line where your thumb ball is located can step in front of the pedal. Don't pedal with your arch, or you will waste your energy.

At home, you can get on the bus and choose the posture that you think is the most standard and will not feel uncomfortable. Ask your family to take a photo of you, and then adjust it according to this photo. When you first go out, you must remember the correct riding posture and correct it at all times, so as to develop a good riding posture, which is good for your future development.

If you think my original answer is helpful, please adopt it. thank you