Okay, let's tackle this question. The question is asking for the average height gain in the first year. Hmm, I remember that infant growth is pretty rapid. Let me think. I think the first year is when they grow the most. So, what's the average? I recall that by the first birthday, a baby usually triples their birth weight, but height... maybe around 25 cm? Wait, birth length is about 50 cm, and by one year, they're around 75 cm? Wait, no, that's weight tripling. Let me check my notes. Oh right, the average height gain in the first year is about 25 cm. So the answer would be 25 cm. Let me make sure. Birth length is approximately 50 cm, and by one year, they're about 75 cm. So that's a gain of 25 cm. Yeah, that makes sense. The options probably include other numbers like 15 cm, 20 cm, 30 cm. The distractors would be incorrect because they don't match the standard growth charts. The key point here is the first year's rapid growth. So the correct answer is 25 cm.

**Core Concept**
Infant growth velocity is highest in the first year, driven by rapid skeletal development. **Average height gain** is a key pediatric growth parameter, with standardized percentiles tracked using WHO growth charts.

**Why the Correct Answer is Right**
The average height gain in the first year is **25 cm**. At birth, infants measure ~50 cm; by 12 months, they reach ~75 cm. This growth is mediated by growth hormone, IGF-1, and thyroid hormones, with nutritional status and genetic factors influencing final height.

**Why Each Wrong Option is Incorrect**
**Option A:** 15 cm is insufficient—this would suggest stunted growth.
**Option B:** 20 cm underestimates the first-year growth spurt.
**Option D:** 30 cm exceeds typical growth, which would indicate pathological gigantism.

**Clinical Pearl / High-Yield Fact**
Remember the **"25 cm rule"**: First-year height gain is 25 cm (from ~50 to ~75 cm). Failure to meet this may signal intrauterine growth restriction or endocrine disorders. Use WHO standards for accurate assessment.

**Correct Answer: C. 25 cm**

✓ Correct Answer: A. 25 cm