[单选题]
An object of mass m is hak:zifcknlz) m7ts,4u7v5 o 3znging by z l xay(o:73a*x:ll zsa string from the ceiling of an elevator. The elevatorsx*l 3l ya7zoxa::l (z is moving upward, but slowing down. What is the tension in the string?
A. less than mg
B. exactly mg
C. greater than mg
D. zero
