Which component acts as a memory element in sequential circuits?

In sequential circuits, the component that acts as a memory element is the flip-flop. Flip-flops are fundamental building blocks used in digital systems to store binary data. They can hold one bit of information and can change their state based on inputs and clock signals, which allows them to retain a value even when the input has changed.

One of the primary functionalities of a flip-flop is to latch onto a value when triggered by a clock signal. This means that flip-flops not only respond to input but also maintain their state until they are prompted to change, thereby providing memory capabilities that are essential for sequential logic.

In contrast to the flip-flop, the other components mentioned serve different purposes. Decoders are used for decoding binary inputs and selecting specific outputs without storing any data. MUX (Multiplexer) is designed for selecting one from multiple input signals and does not have a memory function. Adder circuits perform arithmetic operations on binary numbers but do not have the ability to retain values.

Thus, the flip-flop's ability to store and maintain data makes it the key memory element in sequential circuits.