The correct answer is keep.
The correct answer is (A) To keep (under control, in possession, in mind, in place, etc.); to hold (in place or position); to continue to (use, practice, etc.). Also, to secure the services of (especially by an initial fee)
Retain comes from Old French retenir, Latin retinere.
Examples of use:
- This material will not retain its color if washed
- Although apparently retired, he has retained his directorships.