Transformers in an X-ray machine:?

A is the only correct answer. Transformers don't have filaments or use thermionic emission (that's tubes), and X-rays are generated when electrons collide with a metal target at sufficient velocities, not from mechanical energy. Any transformer will step up or down depending on how it's wired (except a 1:1 transformer, of course, which merely isolates the secondary from the primary).