A frictionless tube is bent into the shape of a semicircle with radius r. The semicircle is tilted so that the diameter makes a fixed angle.
a) The tube's friction affects the semicircle's tilt.
b) The semicircle's radius influences the tube's friction.
c) The semicircle's tilt angle is independent of the tube's friction.
d) The tube's tilt impacts the semicircle's radius.