Alexander Wendt is one of the most important and influential scholars in the constructivist school. He agrees with other constructivists that the structure of the international system is social and that identity is the basis of interests. However, he adopted a systemic approach to show that states’ identities and interests are formed at the system level; in addition, they are endogenous to state interaction. Wendt did not adopt unit level constructivism. The correct answer is E.