**Core Concept**
The development of reaching in infants is a significant milestone in gross motor skills, reflecting neurological maturation and coordination. This process involves the integration of visual, proprioceptive, and motor pathways, ultimately enabling infants to grasp and manipulate objects.

**Why the Correct Answer is Right**
Infants typically begin to develop the ability to reach for objects by around 4 months of age. This is due to improvements in shoulder and arm mobility, as well as the maturation of the corticospinal tract, which facilitates the transmission of motor signals from the brain to the muscles. As infants develop, they progress from a "pincer grasp" (using the thumb and index finger) to a more refined, palmar grasp, enabling them to manipulate objects with greater precision.

**Why Each Wrong Option is Incorrect**
* **Option B:** 6 months is too late for reaching to be a typical developmental milestone, as infants often begin to show interest in objects and develop the ability to reach and grasp by this age, but it is not the earliest age at which this skill is typically observed.
* **Option C:** 8 months is even later than 6 months, and while infants at this age may refine their reaching and grasping skills, it is not the age at which this ability first emerges.
* **Option D:** 10 months is significantly later than the typical age range for the development of reaching in infants, and by this age, most children have already demonstrated this skill.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that developmental milestones can vary significantly among infants, and a delay in reaching or other gross motor skills may indicate the presence of a neurological or musculoskeletal disorder. Regular monitoring of developmental progress and consultation with a pediatrician or specialist are crucial for early identification and intervention.

**✓ Correct Answer: A. 4 months. Infants typically begin to develop the ability to reach for objects by around 4 months of age.**