Respuesta :
D because a 'proxy war' means a war which is instigated (or in other words 'brought about') by major powers that do not become involved. Therefore, the big powers such as USSR and Nazi Germany aided both sides in Spain, however, weren't involved (fighting battles with their own army).
The Spanish Civil War was known as a "Proxy War because both sides in Spain were aided by Nazi Germany and also the U.S.S.R. A Proxy War is when internal wars in a country is aided by an external power. The correct answer is D.