A learner uses "-ing" right, drops it, then fixes it. This shows:

1. Interlanguage can change in a U-shaped pattern. 2. At first the learner uses "-ing" correctly, because it is memorised in chunks with individual words. 3. Later the learner restructures the system around new tense rules and wrongly drops "-ing". 4. Finally, with better understanding of English tense, the learner returns to correct use. 5. The dip looks like regression but reflects growing understanding of grammar. 6. So the pattern shows restructuring of the learner's rule system. **Why the other options fail:** - Fossilization means the system stops developing, but here it recovers. - Loss of the first language is unrelated to dropping "-ing". - Negative transfer would repeat a first-language error, not follow a correct-wrong-correct curve. _Source: Wikipedia, "Interlanguage", section "Stages of development" (revision 1370333900)_