Which of the following is a hypothetical subject that studies alien languages?

Alien languages, i.e. languages of extraterrestrial beings, are a hypothetical subject since none have been encountered so far. The research in these hypothetical languages is variously called exolinguistics, xenolinguistics or astrolinguistics. The question of what form alien languages might take and the possibility for humans to recognize and translate them has been part of the linguistics and language studies courses, e.g., at the Bowling Green State University (2001).

Noam Chomsky (1983), starting with his hypothesis of a genetically-predetermined universal grammar of human languages, held that it would be impossible for a human to naturally learn an alien language because it would most probably violate the universal grammar inborn in humans. Humans would have to study an alien language by the slow way of discovery, the same way as scientists do research in, say, physics.