Final answer:
The ending of a memo may include a summary of the main points of the message. (Option c)
Step-by-step explanation:
The ending of a memo typically includes a summary of the main points of the message. This serves as a conclusion to the memo, ensuring that the recipient understands the key takeaways and important information conveyed in the document. The summary provides a brief recap of the memo's content, helping to reinforce the main ideas and important details for the reader.
While the other options (a, b, and d) are components that can be found within the body of a memo, they are not typically part of the ending or conclusion. Definitions of problems, logical expansions, and supporting data are usually presented in the main body of the memo to provide context, explanation, and evidence for the points being made. The ending of the memo focuses on summarizing and reinforcing the key points for clarity and emphasis.
Therefore, the correct answer is: c. a summary of the main points of the message.