Explain how a vector field F = (f,g,h) is used to describe the motion of the air in a room at one instant in time. Choose the correct answer below. O A. F= (f,g,h) evaluated at (x,y,z) is the velocity vector of an air particle at (x,y,z) at a fixed point in time. O B. The gradient of F= (f.g,h) evaluated at (x,y,z) is the velocity vector of an air particle at (x,y,z) at a fixed point in time. O C. F= (f,g,h) evaluated at (x,y,z) is the location vector of an air particle at (x,y.z) at a fixed point in time. O D. The gradient of F = (f,g,h) evaluated at (x,y,z) is the location vector of an air particle at (x,y,z) at a fixed point in time