If R(t) Is the Position Vector of a Particle in the Plane

Multiple Choice

If r(t) is the position vector of a particle in the plane at time t, find the indicated vector.
-Find the acceleration vector. r(t) = (6 cos t) i + (9 sin t) j

A) a = (6 cos t) i + (9 sin t) j
B) a = (-6 cos t) i + (-9 sin t) j
C) a = (-6 sin t) i + (-9 cos t) j
D) a = (6 sin t) i + (9 cos t) j