Prompt chaining is a fundamental design pattern in LLM application development used to handle complexity. Instead of sending a single, massive, and highly complex prompt to an LLM---which often results in reasoning errors or hallucinations---chaining breaks the logic into a sequence of smaller, targeted steps. For example, a legal assistant might first chain a step to 'identify the legal jurisdiction,' followed by a step to 'extract relevant statutes,' and finally a step to 'summarize the findings.' This modularity improves reliability because each prompt has a narrower focus, making it easier for the model to follow instructions accurately. While it may actually increase latency (contradicting B) and cost (contradicting D) due to multiple API calls, the primary engineering benefit is the significant boost in the quality and robustness of the output. It also allows for intermediate validation and error handling between steps, which is impossible in a single-call architecture.