**Core Concept**
Bidextrous grip, where a newborn can grasp objects with either hand, is a primitive reflex observed in infants during early development. It reflects the immature motor control of the upper limbs and is typically present in the first few months of life before voluntary hand use emerges.

**Why the Correct Answer is Right**
At 4 months, infants exhibit bidextrous grip, meaning they can hold objects with either hand, a reflexive behavior due to the immaturity of the central nervous system’s motor coordination. This reflex is mediated by the spinal cord and is most prominent in the first 3–4 months of life. By 5–6 months, the infant begins to show a preference for one hand, indicating the development of voluntary motor control and hand-eye coordination.

**Why Each Wrong Option is Incorrect**
Option B: At 5 months, infants typically begin to show a preference for one hand, transitioning from bidextrous to unidextrous grip.
Option C: By 6 months, the bidextrous reflex is usually no longer present, and purposeful grasping with one hand dominates.
Option D: At 7 months, infants have fully developed hand preference and are no longer exhibiting bidextrous grip.

**Clinical Pearl / High-Yield Fact**
Bidextrous grip is a normal developmental milestone in the first 4 months of life. Its disappearance by 5 months signals the onset of voluntary motor control and is a key indicator of normal neurodevelopment.

✓ Correct Answer: A. 4 months