**Core Concept**
The question is testing the understanding of developmental milestones in infants, specifically the age at which a baby typically achieves nocturnal continence, also known as being "bed-dry". This concept is related to the maturation of the **urinary bladder** and the development of **neurological control** over bladder function.

**Why the Correct Answer is Right**
Although the exact answer choice is missing, typically, a baby is considered bed-dry around the age of 3-4 years. This is because, by this age, most children have developed sufficient bladder control and neurological maturity to remain dry through the night. The process involves the maturation of the **detrusor muscle** and the development of **cortical control** over the bladder.

**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect if it suggests an age that is too early for nocturnal continence, as most infants are not developmentally ready.
**Option B:** Similarly, if this option suggests an age that is too late, it would be incorrect as most children achieve this milestone earlier.
**Option D:** Without the specific ages, assuming one is significantly earlier or later than the typical range, it would be incorrect based on standard developmental expectations.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that achieving nocturnal continence is a significant developmental milestone, and its delay can indicate underlying issues such as **neurodevelopmental disorders** or **urological problems**.

**Correct Answer:** Correct Answer: C. 3 years.