## Core Concept
The question assesses the developmental milestones of an 8-week-old infant, focusing on physical and motor skills. At this age, infants typically exhibit certain reflexes and abilities while lacking others. Understanding these milestones is crucial for pediatricians to evaluate infant development.

## Why the Correct Answer is Right
An 8-week-old infant is expected to have certain primitive reflexes and developmental skills. For instance, they should be able to lift their head while on their stomach (somewhat), bring their hands to the midline of their body, and exhibit the rooting reflex. However, complex motor skills like sitting without support or walking are not expected at this age.

## Why Each Wrong Option is Incorrect
- **Option A:** Typically, an 8-week-old infant can exhibit a **rooting reflex**, which is a natural reflex that helps with feeding. When the cheek or lips are stroked, the infant turns their head towards the stimulus. This reflex is present and correct at this age.
- **Option B:** Infants at this age can usually **bring their hands to the midline** of their body, which is an important developmental milestone indicating neurological development.
- **Option D:** The **grasp reflex** is also present at this age, where an infant will grasp a finger placed in their palm.

## Clinical Pearl / High-Yield Fact
A key developmental milestone to remember is that by 8 weeks, infants should be able to **lift their head to about 45 degrees** while on their stomach. Not being able to do so might indicate a developmental delay.

## Correct Answer: D.