Answer: The correct answer is
b. Memos are commonly written to people within your own organization.
Explanation: Memos are written form of communication in a formal setting. They are written to people within the same organisation.
Memos contain a 'from' and 'to' headings as well as a subject. This helps give the receiver a clear picture of the purpose of the communication as often times the reader skims through the memo to get a clue of the content.