**Core Concept:** The development of fine motor skills, including drawing geometric figures like a cross, is an important milestone in child development. This milestone represents the child's ability to control their hand movements and manipulate objects accurately. Fine motor skills are essential for writing, drawing, and performing daily activities.

**Why the Correct Answer is Right:** The correct answer should be based on the typical age range for achieving fine motor skills milestones in a child's development. Fine motor skills typically develop between 2 to 5 years of age. In this case, Option D (5 years) is the correct answer as it corresponds to the typical age when a child can accurately draw a cross, indicating the development of fine motor control.

**Why Each Wrong Option is Incorrect:**

A. 4 years: Fine motor skills may develop slightly earlier, but drawing a cross is an advanced skill that requires coordination and control, and may not be achieved by all children at 4 years old.
B. 3 years: Fine motor skills start developing at around 2 years, but drawing a cross is an advanced skill not typically achieved by all children at 3 years old.
C. 2 years: Fine motor skills start developing at around 2 years, but drawing a cross is an advanced skill not typically achieved by all children at 2 years old.

**Why the Correct Answer is Right:** Children's motor skills develop gradually as they grow older, and drawing a cross is an advanced skill that requires coordination and control. At 5 years old, children are generally more developed in their fine motor skills, allowing them to perform this task accurately.

**Clinical Pearl**: Monitoring a child's development in fine motor skills is essential for identifying potential developmental delays or disabilities and guiding appropriate interventions. In clinical practice, pediatricians or developmental pediatricians might assess a child's fine motor skills to evaluate their overall development and identify potential issues.

**Correct Answer:** D. 5 years.