For the relativity one, momentum at relativistic speeds is p = γm0v. Since the only thing changing between the particles is m0, it was the alpha particle because it has the largest rest mass. The Lorentz factor is determined by relative velocity which would be the same across all particles.
Unfortunately, I haven’t studied optics or waves that much because they aren’t covered in AP Physics C. For the radiation question, I was stuck between wireless router and smoke detector.