6. Which object listed below is not accelerating?

Question

a.) A person standing on the surface of the Earth.
b.) A satellite in geostationary orbit.
c.) A jet traveling at Mach 6.7 in a straight line.
d.) A child standing on a merry-go-round.
e.) A block oscillating on a spring when it reached its maximum amplitude.

c is a good guess, but a is not accelerating much either. Whether a jet is going in a straight line depends upon the coordinate system used. In a true inertial coordinate system, it is accelerating too