Which purpose of configuring perfect Forward secret is true?

A.
For every negotiation of a new phase 1 SA, the two gateways generate a new set of phase 2 keys.

B.
For every negotiation of a new phase 2 SA, the two gateways generate a new set of phase 1 keys.

C.
For every negotiation of a new phase 1 SA, the two gateways generate a new set of phase 1 keys.

D.
For every negotiation of a new phase 2 SA, the two gateways generate a new set of phase 2 keys.