The Arithmetic Mean (AM) of two positive numbers $a$ and $b$ is

1. NCERT §8.4 (Means): the Arithmetic Mean of $a$ and $b$ is half their sum. 2. $\text{AM} = \dfrac{a + b}{2}$. 3. Geometric interpretation: AM is the AVERAGE of two values — what you intuitively call the midpoint on a number line. 4. Option A is the Geometric Mean (GM). Option C is the Harmonic Mean (HM). Option D has no standard mean interpretation. 5. By the AM-GM inequality: $\text{AM} \geq \text{GM}$ with equality iff $a = b$. So AM is always the largest of the three classical means. _Source: NCERT Class 11 Mathematics, Ch 8, §8.4 (Arithmetic Mean), p. 9._