The answer is C: Taking credit for work that your colleague completed, so you can impress your boss.
Explanation for each option:
a) Getting permission to use a client list from your old job to approach potential investors: This action is not typically supported by egoism, as it involves obtaining permission, which suggests a consideration for ethical standards and respect for others' property. Egoism would more likely support using the list without permission if it benefits oneself.
b) Joining with coworkers to let a new employee know you disapprove of his hire, even though you'll get in trouble: This action is not supported by egoism because it involves taking a risk of getting in trouble, which does not align with the self-interest focus of egoism. Egoism would prioritize actions that benefit oneself without negative consequences.
c) Taking credit for work that your colleague completed, so you can impress your boss: This action is supported by egoism because it directly benefits the individual by enhancing their reputation and standing with their boss, even though it is unethical as it involves dishonesty and undermines a colleague.
d) Introducing a friend to your favorite weight-loss supplement when he wants to lose weight: This action is generally ethical and does not align with egoism in a way that seems unethical. It involves helping a friend, which may not directly benefit oneself unless there is a hidden self-interest, such as financial gain from promoting the supplement.