With PGP, which of the following entity signs a user’s public key?

A.
The receipient of the message.

B.
A third party that belong to what’s often known as “web of trust”, that can verify the relationship between the user and the key.

C.
The sender of the message.

D.
The vendor of the PGP program.

E.
The sender’s administrator who provides the sender with the PGP program.