A Ferris wheel is turning about a horizontal axis through its center. The linear speed of a passenger sitting on the rim is constant. Which one of the following sentences about the passenger's acceleration is correct?
a) Its magnitude at the highest point is higher than at the lowest point, and it is downwards at both points.
b) Both its magnitude and direction are the same at the highest and at the lowest points.
c) Its magnitude is the same at the highest and at the lowest points, but the directions are opposite.
d) Its magnitude at the highest point is smaller than at the lowest point, and it is downwards at both points.