Which type of load has a resistance that remains unchanged with varying voltage?

A passive load is characterized by having a resistance that remains unchanged regardless of the voltage applied across it. This means that for a passive load, the relationship between voltage and current is defined by Ohm's Law (V = IR), where V is voltage, I is current, and R is resistance. As long as the resistance remains constant, the load will behave predictably under different voltage conditions, making it easier to manage and design circuits with these loads.

In contrast, other types of loads can exhibit different behaviors. An active load typically involves components that can control current or voltage actively, such as transistors or operational amplifiers, and can change their resistance based on the conditions of the circuit. A dynamic load refers to a load that varies over time, typically with complex input conditions, meaning its resistance can change under different operating circumstances. A variable load is designed to change its resistance intentionally in response to control signals, which means it does not maintain a constant resistance. Hence, the defining characteristic of a passive load makes it the correct answer in this context.