Answer:
1. Informal
2. Formal
3. Informal
4. Informal
5. Formal
6. Informal
7. Informal
8. Informal
9. Informal
10. Formal
Step-by-step explanation:
Formal is used when addressing someone of higher authority or someone you do not know. Sentences are in proper English and words are not in short form.
Informal is used when addressing someone you are familiar with like a family member or friend. Sentences may have words in short form.