The correct answer is B. Increases.
The ionization potential of an atom is the amount of energy required to remove an electron from the atom. As we move from left to right in a period, the atomic number increases and the number of protons in the nucleus increases. This means that the electrons are held more tightly to the nucleus and more energy is required to remove them. Therefore, the ionization potential increases across a period.
Option A is incorrect because the ionization potential can be predicted. It increases across a period.
Option C is incorrect because the ionization potential does not decrease across a period. It increases across a period.
Option D is incorrect because the ionization potential does not remain the same across a period. It increases across a period.