Scientific name of sunn hemp is
Crotalaria juncea
Crotolaria juncea, commonly known as sunn hemp, Indian hemp is a tropical Asian plant belonging to legume family Fabaceae.. It is generally considered to as originated in Indian. It is now widely grown throughout the tropics and subtropics as a source of green manure, fodder and lignified fibre. It is also used as biofuel. It is an annual plant and it is an important summer cover crop in the United States. Hence, the scientific name of Sunn hemp is Crotalaria juncea. So, the correct answer is 'Crotalaria juncea'.