Which of the Following Is True of Subagents

Which of the following is true of subagents?

A) They must be appointed by the principal,though they report to the agent.
B) They are considered to be agents of the agent,but not of the principal himself.
C) Subagents do not have the authority to bind a principal,but can bind the agent.
D) For a subagency to exist,an agent must have the authority to make the subagent his agent.