Which adjective would best fit a strict policy?

The adjective "harsh" aligns perfectly with the notion of a strict policy. Strict policies are usually characterized by their rigidity and adherence to rules, often without leniency or exceptions. Such policies create a framework that is inflexible and demanding, which is captured well by the term "harsh."

While options like "flexible" and "tolerant" convey an openness to change or consideration of different circumstances, they directly contradict the essence of a strict policy. Similarly, "ambiguous" suggests vagueness or a lack of clarity, which is contrary to the precision and definiteness typically associated with strict rules. Therefore, "harsh" is the most fitting choice, as it effectively communicates the stringent and uncompromising nature inherent in strict policies.