If a Supersonic Plane Is Flying at Increasing Speed as the Temperature

Multiple Choice

If a supersonic plane is flying at increasing speed as the temperature decreases, what happens to the Mach number in this instance?

A) It stays the same.
B) It increases.
C) It decreases.
D) It can do any of the above.
E) It can do either (a) or (b) but not (c) .