To reduce Azure OpenAI costs with minimal quality loss, you target the biggest cost drivers: token usage and model price per token (or throughput unit). C (Optimize the prompts) is a best practice because shorter, clearer prompts reduce unnecessary input tokens and often reduce output length by tightening instructions and formatting. Prompt optimization can preserve or even improve quality by removing ambiguity, adding constraints, and using compact context (for example, only the most relevant grounding passages). Lower token consumption directly lowers cost while maintaining response usefulness.

D (Switch to an alternate model) is also effective because different models have different price/performance tradeoffs. Moving from a premium model to a more cost-efficient model (or a smaller variant) can significantly reduce spend. You can minimize quality impact by validating outputs on representative scenarios and using a tiered approach (cheap model by default, expensive model only for complex cases).

The other options are less aligned to the goal. A (Fine-tune) typically increases cost (training and ongoing evaluation) and is not the first-line cost reducer. B (Content moderation) is primarily a safety control; it can add overhead and doesn't directly reduce token costs. E (Decrease hosting hours) applies to capacity-based hosting scenarios, but the question states a prebuilt Azure OpenAI model for content generation---cost reduction is best achieved by prompt/token optimization and selecting the right model.