An ELL overgenerates the regular past tense -ed to irregular verbs. This indicates what process?

The correct answer signifies that the English Language Learner (ELL) has begun to internalize a rule of forming the past tense by adding -ed to verbs. This is a common occurrence in language acquisition where learners apply grammatical rules they have learned to all verbs, including those that are irregular.

By overgeneralizing, the ELL demonstrates that they understand the structure of regular past tense formation but may not yet have fully grasped the exceptions represented by irregular verbs. This process reflects a developmental stage in language learning where learners are experimenting with and practicing language rules they've been exposed to, showing their learning progress and increasing proficiency in the language.

The other options focus on different aspects of language learning. Memorizing vocabulary pertains to acquiring individual words rather than grammatical structures, misunderstanding syntax deals with incorrect sentence construction rather than verb forms, and applying phonetic rules relates to the sounds of language instead of grammatical applications. Thus, the selected answer accurately captures the essence of the overgeneration phenomenon as a reflection of the learner's developing understanding of grammar.