Correct Answer: C

Rationale: The development of a pincer grasp reflects fine motor skills, which develop in a proximodistal pattern (from the center of the body outward).

Correct Answer: A

Rationale: Rotavirus is the most common cause of diarrhea in young children, particularly those under the age of 2. Giardia, Shigella, and Salmonella can also cause diarrhea, but in the context of young children, Rotavirus is the primary pathogen responsible for diarrheal illnesses.

Correct Answer: B

Rationale: At 2 months, infants typically react to loud noises with the Moro reflex, a startle response that is normal at this stage of development.

Correct Answer: B

Rationale: In the management of acute sickle cell pain crisis in children, morphine is the preferred medication due to its effectiveness in providing pain relief. Meperidine (Demerol) is less commonly used in this scenario because of its potential for neurotoxicity with repeated doses. Acetaminophen (Tylenol) and Ibuprofen (Motrin) are not typically sufficient for managing the severe pain associated with sickle cell crises and are not the first-line treatment options.

Correct Answer: B

Rationale: Infants typically begin to smile in response to pleasurable stimuli by 2 months, which is an early sign of social interaction and emotional development.