Okay, the user wants me to translate "sub-grade" into Korean. Let me think about the correct term here. "Sub-grade" can have different meanings depending on the context. In construction or civil engineering, it might refer to the subgrade, which is the layer of soil or rock that supports a structure. In that case, the Korean term would be "하부 지반" or "기초 지반".
Alternatively, if it's related to education or grading, "sub-grade" might mean a lower grade or a subsidiary grade. Then the translation could be "하위 등급" or "부등급". But since the user didn't provide context, I should consider the most common usage.
Looking up "sub-grade" in Korean, the primary translation in engineering contexts is "하부 지반". However, if it's a term used in another field, the translation might vary. Since the user's previous message was just "ok" and the initial instruction was to translate all content into Korean unless it's already in Korean, I need to stick to the most likely translation.
I should check if "sub-grade" is a technical term. Yes, in construction, it's commonly used. So the safest bet is "하부 지반". But I should also consider if there's a more standard term. Maybe "기초 지반" is more commonly used. Wait, "subgrade" in Korean is often translated as "하부 지반" or "기초 지반" depending on the context.
Since the user hasn't provided additional context, I'll go with the most standard translation. Let me confirm with a quick check. Yes, "하부 지반" is the standard term for sub-grade in engineering. So the translation should be "하부 지반".