Which system is responsible for purifying the body by eliminating waste matter?

The excretory system is primarily responsible for purifying the body by eliminating waste matter. It includes the kidneys, ureters, bladder, and urethra, which work together to filter blood, remove waste products, and regulate water and electrolyte balance in the body. This system plays a crucial role in maintaining homeostasis, ensuring that harmful substances do not accumulate in the body and that necessary fluid levels are maintained for optimal function.

In contrast, the digestive system focuses on breaking down food, absorbing nutrients, and expelling undigested food. The circulatory system is responsible for transporting blood, nutrients, gases, and hormones throughout the body but does not directly eliminate waste. The nervous system's primary function is to control and coordinate body functions through signals and responses, but it does not play a direct role in waste elimination. Thus, the excretory system’s specific function in waste removal confirms it as the correct response to the question.