[单选题]
A box with a mass of M -bs4fqq9zrm j o 9aa8/rests on a balance in a3h)7 ze-ueyvyn elevator that is moving downwards. The elevator slows with 7hu)- 3zyeevy an acceleration of $\frac{g}{4}$.
Which of the following gives the reading of the balance?
A. $\frac{5Mg}{4}$
B. $Mg$
C. $\frac{3Mg}{4}$
D. $\frac{Mg}{2}$