Answer:
c. a competitor's confidential memos.
Explanation:
Using a competitor's confidential memos for external analysis is not an ethical practice. To use confidential internal memos is unethical and it might be illegal in some situations because you might use an illegal and unethical way to obtain that information. All the other options Trade shows, Advertisements and annual report are the publicized data which could be used. Competitive Intelligence is a practice in the market to to gather competitor's data by using all the public information available which is legal and ethical too.
