The verified answer is B. Chain-of-thought prompting. The requirement is for the GenAI application to explain reasoning steps before providing final answers. AWS prompt-engineering guidance identifies chain-of-thought prompting as a technique used for logical reasoning and complex problem solving. AWS guidance also recommends considering chain-of-thought or tree-of-thought prompting for logical reasoning tasks.

Chain-of-thought prompting encourages the model to work through intermediate reasoning steps before producing a final response. That matches the question exactly. The phrase “explain its reasoning steps before giving final answers” is the defining clue.

Few-shot prompting is incorrect because it provides examples of the desired input-output pattern. AWS describes few-shot prompting as including a few examples to help a model calibrate its output to meet expectations. It can guide tone, format, or task structure, but it is not specifically the technique for step-by-step reasoning.

Prompt templating is incorrect because a prompt template standardizes reusable prompt structure. Templates can include variables, instructions, and formatting rules, but the technique itself does not specifically require the model to reason step by step.

Zero-shot prompting is incorrect because it gives the model an instruction without examples. AWS guidance describes zero-shot prompting as a prompt with no example input-output pair. It is useful for direct tasks, but it does not specifically meet the reasoning-step requirement.

Because the application must explain intermediate reasoning before the final answer, the correct technique is chain-of-thought prompting.