Final answer:
A manipulative individual is most likely to have successfully blackmailed someone as they have the traits that enable them to influence and control others unethically. Ethical, trustworthy, and honest personalities are contrary to the deceitful nature of blackmailing.
Step-by-step explanation:
The question "Who has probably successfully blackmailed someone?" relates to the characteristics of individuals who might engage in such unethical behavior. Blackmail involves threatening to reveal information about a person unless they meet certain demands, often for personal gain.
In this case, the most likely answer is b. Manipulative individual. Ethical, trustworthy, and honest people are generally characterized by their adherence to moral principles, transparent behavior, and reliability; these traits would deter them from engaging in blackmail, which relies on deception and manipulation. On the other hand, a manipulative person is skilled in influencing or controlling others to their advantage, often at the expense of ethics.