There is a slight error in the title of this question :)
Instead of ‘if my dad would let me’, it’s ‘had my dad let me (remember this useful phrase ending). This is because you can’t have a double ‘would’ in the same phrase.
The correct answers to the questions are:
3. D. Theirs - This is the third person plural possessive.
4. A. Common - This is the kind of adjective that is used most frequently in ordinary speech or writing.
5. B. object - This is what a noun that completes an action is called.
Thank you for posting your question. I hope that this answer helped you. Let me know if you need more help.