[单选题]
A mass is attached to a,rpi nxu fb)62 9zox+r vertical spring and bobs up and down between pointr+ez/jy; 0 pbes A and B. Where is thep byz+/0; reej mass located when its kinetic energy is a minimum?
A. at either A or B
B. midway between A and B
C. one-fourth of the way between A and B
D. none of the above