In an adiabatic process, no heat is exchanged with the surroundings. According to the first law of thermodynamics and for an ideal gas undergoing adiabatic expansion, the product of pressure and volume, \( P \cdot V \), decreases. This is because, as the gas expands, its pressure decreases and its volume increases, but the rate at which the volume increases is slower than the pressure decreases, leading to an overall decrease in the product of \( P \) and \( V \).
So, the correct answer is (A): Decreases