Which of the following is classified as a tuber vegetable?

The potato is classified as a tuber vegetable because it is an underground storage organ of the plant and primarily serves as a means of storing energy in the form of starch. Tubers develop from the root systems of certain plants and are characterized by their swollen, fleshy structure that acts as both a food source and a means of vegetative reproduction.

In contrast, broccoli is a flowering vegetable belonging to the Brassica family, while carrots, though they do have a similar appearance in terms of being root vegetables, are classified as taproots and not tubers. Spinach is a leafy green and does not fall under the category of root or tuber vegetables. Each of these classifications highlights the plant's purpose and characteristics that distinguish them from one another.