[单选题]
A mass is attached to a verml:fm.x2 57qg u hg-cntical spring and bobs up06)ovqdbk x8a h1rb3 z and down between points A and B. Where is the mass located when its kinetic energyb6bo38z) x 1akdv0 qhr 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
