Here are the corrections for each sentence:

1. **Correction**: "your" should be "your first day" (it should be "What is your first day at school, Duong?").
2. **Correction**: "doesn’t have" is correct; this sentence is fine.
3. **Correction**: "is" should be removed; it should be "My cousin’s school has 7 classes..."
4. **Correction**: "always" is correct, but "but" should be changed to "and"; it should read "She is always punctual, and her friend is always late."
5. **Correction**: "do" is correct, this sentence is fine.

The phrases needing correction are 1 (A) and 3 (C).