After Grotius, scholars of international law came to be classified under one of three schools: 1) Naturalists, such as Samuel von Pufendorf (1632-1694), who based international law on natural law exclusively; 2) Positivists, such as Cornelius van Bynkershoek (1673-1743), who based it on the consent of States that was evidenced in State practice, and 3) Grotians (followers of Grotius), including Christian Wolff (1679-1754) and Emmerich de Vattel (1714-67), who relied on both natural law and the consent of States as well as reiterated that international law was binding on States. The correct answer is D.