Correct answer: C. Because it imposes a strict condition
Explanation: Direct answer: Option C, because it imposes a strict condition. A rule is a specific and compulsory instruction. The statement ‘refund will not be given without the original bill’ leaves little or no discretion: if the original bill is absent, the refund must be refused. Step by step: identify the required document; check whether it is present; if it is absent, apply the stated consequence. Option A is wrong because broad guidance is the nature of a policy, not this fixed condition. Option B is wrong because the statement reduces discretion rather than increasing it; the employee cannot freely decide whether to make an exception. Option C is correct because it describes the compulsory, definite character of the statement. Option D is wrong because this is a customer-service condition, not a market strategy for competition, pricing or promotion. A policy may guide an employee to consider circumstances, while a rule gives a clear yes-or-no requirement. Memory cue: words such as ‘must,’ ‘only if,’ and ‘without this, no service’ often signal a rule.