[单选题]
A block of mass $m$, initially at rest, is acted upon by two unequal forces $F_1$ and $F_2$ such that $F_1>F_2$ as shown in the diagram below. The forces act for a time $t$.
Which of the following correctly represents the magnitude of the final velocity of the block after time $t$?
A. $(\frac{F_1+F_2}{m})(t)$
B. $(\frac{F_1-F_2}{m})(t)$
C. $(\frac{F_2-F_1}{m})(t)$
D. $(\frac{F_1-F_2}{t})(m)$
