Which of the following plants is a pasture legume?

Stylosanthes gracilis is a pasture legume. Pasture legumes are important components of grazing systems because they provide high-quality forage for livestock and can also fix nitrogen in the soil, which benefits the growth of other plants in the pasture. Stylosanthes gracilis is a tropical and subtropical legume that is commonly used in grazing systems due to its high protein content and ability to grow well in poor soil conditions. It is also drought-tolerant and can grow in areas with low rainfall. The other options listed, namely Cynodon pletostachyus, Panicum maximum, and Pennisetum purpureum, are all grass species commonly used in grazing systems, but they are not legumes.