By emitting X-rays, an atom

Explanation

When an atom emits X-rays, it does so by an electron transitioning from a higher energy level to a lower one, typically from an outer shell to an inner shell. This transition releases energy in the form of X-rays, which are high-energy electromagnetic radiation. The correct answer is that the atom attains the ground state (Option A), as it moves to a lower energy configuration. Options B, C, and D are incorrect as they misinterpret the nature of the transitions involved in X-ray emission. Option B suggests an increase in energy, which is contrary to the emission process. Options C and D are related to ionization, which involves electron removal rather than internal transitions that result in X-ray emission.