Answer: a. durable power of attorney.
Step-by-step explanation:
A durable power of attorney gives a person the legal right to act on the behalf of another person such that the former will be able to handle the affairs of the latter. A durable power of attorney stays in effect even when a person is declared incapable of managing their own affairs.
It is therefore the best option for Preet here because with him being away for a little while, his sister can take care of his affairs as he is unable to do so himself and when he is back, he can simply remove his sister from the position as it is not a complicated process.