The key schedule results in generating multiple keys from the one secret key. These multiple keys are used?

(A)		in multiple sessions of communications one after the other. For example, if someone has 12 keys, they can use it for twelve video calls one after the other.
		(B) such that one of them is picked up at random at a time.
	(C)	some as private keys, some as public keys.
	(D)	for different rounds of encryption for the same plaintext to strengthen the cipher.