Which of the following describes an electrolyte?

An electrolyte is fundamentally defined as a solution that conducts electricity. This property arises from the presence of ions in the solution, which are charged particles that can move freely and carry an electric current. In biological systems, electrolytes include essential ions such as sodium, potassium, calcium, and magnesium, all of which play crucial roles in various physiological functions, including nerve signal transmission and muscle contraction.

The other options describe unrelated concepts that do not pertain to the definition of an electrolyte. A nutrient necessary for vision mainly refers to substances like vitamin A, which is essential for eye health and function. A substance that prevents infection typically relates to antimicrobial agents or antibiotics, which do not conduct electricity. Lastly, muscle tissue types refer to the classification of muscles in the body, such as skeletal, cardiac, or smooth muscle, which are not directly related to the electrical properties associated with electrolytes.