If you must jump from a ship，your posture should include（）.

A. holding down the life preserver against the chest with one arm crossing the other，covering the mouth and nose with a hand，and feet together
B. knees bent and held close to the body with both arms around legs
C. body straight and arms held tightly at the sides for feet first entry into the water
D. both hands holding the life preserver below the chin，with knees bent，and legs crossed