If the voltage remains constant in a circuit and the resistance is increased, the current will decrease. This is described by Ohm's Law, which states that \( I = \frac{V}{R} \), where \( I \) is the current, \( V \) is the voltage, and \( R \) is the resistance. Since \( V \) is constant and \( R \) is increasing, the current \( I \) will decrease.
So the correct answer is: B) decrease.