Which hypothesis asserts that grammar structures follow a natural order during language development?

The Natural Order Hypothesis is the correct choice because it specifically posits that language learners acquire grammatical structures in a predictable, natural sequence, regardless of the learner's first language. This hypothesis suggests that certain grammatical features are acquired before others, which remains consistent across different learners and contexts. For instance, many learners tend to grasp basic sentence structures before mastering more complex grammatical forms, indicating a natural progression in language acquisition.

The focus of this hypothesis is on the sequencing of grammatical forms that learners encounter and internalize over time, emphasizing that this development occurs independently of direct teaching strategies or the complexity of materials presented to the learner. By understanding this hypothesis, educators can better structure their teaching to align with the natural tendencies of language acquisition, facilitating a more effective learning environment for English language learners.