Which theory suggests that language acquisition occurs in stages?

Krashen's Input Hypothesis is the correct answer because it specifically emphasizes the stages of language acquisition through comprehensible input. According to this theory, learners acquire language best when they receive input that is slightly above their current proficiency level, allowing them to progressively understand and assimilate more complex structures. This model suggests that language acquisition happens in a natural, developmental way, where learners move through various stages as they become more proficient.

Other theories mentioned do not necessarily focus on stages of language acquisition in the same way. The Behaviorist Theory emphasizes reinforcement and imitation rather than stages of development. Constructivist Theory highlights the importance of social interaction and building knowledge but does not outline specific stages of language acquisition. Cognitive Development Theory, initially developed by Piaget, is concerned with the overall cognitive development in children and does not specifically address language acquisition stages. Each of these theories provides valuable insights into learning but lacks the specific framework of stages outlined in Krashen's Input Hypothesis.