【正确答案】正确答案：Input hypothesis proposed by Krashen, holds that language acquisition takes place when a learner understands input that contains grammatical forms that are at " i + 1" (i. e. are a little more advanced than the current state of the learner's interlanguage). In other words, language acquisition depends on comprehensible input. Interaction hypothesis by Michael Long, also emphasizes the importance of comprehensible input but claims that it is most effective when it is modified through the negotiation of meaning.