**Core Concept**
Motor development in children follows a predictable sequence, with specific gross motor skills emerging at defined ages. The ability to perform tasks like skipping, walking on heels, hopping, and tandem gati (walking in a straight line with feet together) reflects the maturation of the central nervous system and coordination, typically achieved by age 4 years.

**Why the Correct Answer is Right**
By 4 years of age, most children have developed sufficient motor coordination to perform these gross motor tasks. Skipping, heel-to-toe walking, hopping, and tandem gati are considered milestones in gross motor development that are expected to be mastered by this age. Delay in these functions suggests possible neurodevelopmental delay, cerebral palsy, or other underlying conditions affecting motor control and balance.

**Why Each Wrong Option is Incorrect**
Option A: 3 years – At this age, children typically master basic walking and simple movements but not complex coordination like skipping or tandem gati. These skills are not yet expected to be fully developed.
Option C: 6 years – By 6 years, most children have already mastered these skills, so this is too late for a developmental delay assessment.
Option D: 8 years – This is well beyond the expected developmental timeline; such motor skills are routinely achieved by age 4–5.

**Clinical Pearl / High-Yield Fact**
The 4-year milestone is a key benchmark in pediatric motor development. If a child fails to perform these tasks by age 4, it raises concern for neurodevelopmental disorders and warrants further evaluation including neurological and developmental assessments.

✓ Correct Answer: B. 4 years