Correct Answer: Affix

Solution : The correct choice is the third option.

Affix means to attach or fasten something securely to another object. It aligns closely with the meaning of "fasten", which involves securing or joining things together.

The meanings of the other options are:

• Detach : To separate or disconnect something.
• Release : To set free or let go.
• Loosen : To make something less tight or secure.

Therefore, the right answer is affix.