C.

This was a tough quiz, but according to the Centers for Disease Control, the top five most nutrient-rich vegetables are (in order): watercress, Chinese cabbage (so-called Napa cabbage is a familiar type of Chinese cabbage), chard, beet greens, and spinach. Artichokes, alas, do not make the cut. A vegetable’s “nutrient density score” is a measure that evaluates the amount of essential nutrients in a food relative to its calorie content. Watercress scores a perfect 100!