An increase in kVp increases the :: (A) Number of photons generated, (B) Their mean energy, (C) Their maximal energy, (D) All of the above
Answer is D. Increasing the kVp of an x-ray machine increases:

The number of photons generated.
The mean energy of the photons.
The maximal energy of the photons.

Ref:Ref: Oral Radiology, Principles and Interpretation / Stuart C. White, Michael J. Pharoah - 7th ed - pg - 10