How does 3DES use the DES algorithm to encrypt a message?

A.
encrypts a message with K1, decrypts the output with K2, then encrypts it with K3

B.
encrypts a message with K1, encrypts the output with K2, then encrypts it with K3

C.
encrypts K1 using K2, then encrypts it using K3, then encrypts a message using the output key

D.
encrypts a message with K1, encrypts the output with the K2, then decrypts it with K3

Explanation: