In the Equation $\vec { M } + \vec { v } = \vec { P } + \vec { Y } _ { R }$

In the equation $\vec { M } + \vec { v } = \vec { P } + \vec { Y } _ { R }$ , what does $\vec { v }$
Stand for?

A) the velocity of money
B) growth in the velocity of money
C) the market value of goods and services
D) growth in the market value of goods and services