NCERT: form-focused teaching widened the gap between linguistic age and:

1. The structural approach was form-focused: it taught structures one by one. 2. Learners who could make correct sentences still could not use language in real situations. 3. Form-focused teaching aggravated the gap between the learner's linguistic age and mental age. 4. The mind could no longer be engaged by such language work. 5. The gap is therefore between what the learner can say and what the learner can think. 6. So the answer is linguistic age and mental age. **Why the other options fail:** - Reading age measures reading skill only, not the gap NCERT names. - Calendar age is simply age in years, which form-focused teaching does not change. - Grade level is the class a learner is in and is not an age at all. _Source: NCERT, Position Paper of the National Focus Group on Teaching of English (2006), section "1.2.3 ELT (English Language Teaching) in India", PDF p. 12 (ncert.nic.in/pdf/focus-group/english.pdf)_