NCP-GENL Prompt Engineering Practice Question
An engineer is building a customer-facing FAQ bot using an NVIDIA NIM-hosted Llama 3.1 70B model. The bot must answer ONLY from a supplied product knowledge base and must respond with 'I don't have that information' when the answer is not present. Which prompt engineering approach BEST enforces this constraint?
⚠ Common exam trap
The trap here is assuming that lowering temperature or top_p will prevent hallucination, when grounding actually depends on explicit instructions and delimited context, not on sampling parameters.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Instruct the model to answer only from the provided knowledge base, explicitly state that it must reply with the refusal phrase when the answer is absent, and include the knowledge base inside clearly delimited sections.
Grounded FAQ bots need an explicit behavioral contract: what source to use, what to do when the source lacks the answer, and clear separation of context from user input. Delimiters prevent prompt injection from blending with instructions, and a fixed refusal phrase makes the fallback deterministic and testable. Sampling parameters alone cannot enforce scope constraints.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Instruct the model to answer only from the provided knowledge base, explicitly state that it must reply with the refusal phrase when the answer is absent, and include the knowledge base inside clearly delimited sections.
Why this is correct
Combining an explicit grounding instruction, a mandated refusal string, and clearly delimited context gives the model a precise behavioral contract. The delimiters separate trusted context from user input, while the refusal phrase defines the exact fallback behavior. This is the most reliable prompt-level method to constrain an NIM-hosted model to grounded answers without retraining.
- ✗
Set the top_p value to 0.1 and rely on the model's pretrained knowledge of the product domain instead of supplying the knowledge base in the prompt.
Why it's wrong here
Relying on pretrained knowledge does not guarantee the model knows this specific product's current details, and low top_p only narrows token sampling, it does not ground factual content. The bot would answer from stale or invented information and would not reliably emit the required refusal phrase when data is missing.
- ✗
Append the entire knowledge base to every user message without any instruction about scope or refusal behavior, letting the model infer the rules from context.
Why it's wrong here
Providing context without explicit scope and refusal rules leaves behavior undefined. The model may blend knowledge-base facts with pretrained assumptions or answer questions outside the document's scope. Without a mandated fallback phrase, responses become inconsistent and the 'I don't have that information' contract is not enforced.
- ✗
Increase the temperature to 1.0 and add 'Be creative and helpful' to the system prompt so the model can improvise when the knowledge base is incomplete.
Why it's wrong here
Raising temperature increases sampling randomness, which directly encourages the model to invent plausible but ungrounded answers. The instruction to 'be creative' conflicts with the requirement to answer only from the knowledge base. This combination maximizes hallucination risk and cannot enforce the refusal behavior the FAQ bot requires.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official NVIDIA exam blueprint
This NCP-GENL practice question is part of Courseiva's free NVIDIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the NCP-GENL exam.