Stephen Krashen’s theory of second language acquisition consists of five main hypotheses, not six. These hypotheses are:
1. The Acquisition-Learning Hypothesis – Language acquisition (subconscious) and language learning (conscious) are distinct processes.
2. The Monitor Hypothesis – Learners use conscious knowledge of rules to monitor their output, but this should not interfere with natural communication.
3. The Natural Order Hypothesis – Language acquisition follows a predictable sequence, regardless of the learner’s first language.
4. The Input Hypothesis – Learners acquire language when they receive comprehensible input slightly beyond their current level (i+1).
5. The Affective Filter Hypothesis – Emotional factors such as motivation, anxiety, and self-confidence affect language acquisition.
The Writing Hypothesis is not one of Krashen's hypotheses, making option 4 the correct answer.