Answer: c) Principle of duties.
Step-by-step explanation:
Principle of duties describes that morality of any task or act is considered on basis of right or wrong being under control of obligation and regulation.As per rules, any action violating and damaging rules should be considered wrong act and should be reported and corrected.
According to t question, Tim should base his suspicion reporting thought as method of following principle of duties.He is aware about his duty as per organization and its regulation .So, reporting about reimbursement request without receipt and various suspicious undocumented task going in organization to authorities is making him follow moral of the duties.
Other options are incorrect because principle of egoism, principle of virtues and principle of utility is not used by Tim for his suspicion. Thus, the correct option is option(c).