**Core Concept**
Newborns and neonates often present with various physiological adaptations and transient conditions that are distinct from their adult counterparts. These conditions arise due to the immaturity of their systems and the process of transition from fetal to extrauterine life.

**Why the Correct Answer is Right**
Erythema toxicum neonatorum (A) is a benign, self-limiting condition characterized by the appearance of small, yellowish or white bumps on the skin, often accompanied by erythema. It is thought to be an allergic reaction to environmental stimuli. Transitional stools (B), also known as meconium-ileus-like syndrome, occur when the meconium is not fully cleared from the intestine, leading to a mixture of meconium and bile-stained stools. Mongolian spots (C) are congenital melanocytic lesions that are flat, blue or blue-gray in color, and are most commonly found on the lower back, buttocks, or sacral region. These conditions are all common in neonates and do not require specific treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** Erythema toxicum is not a disease or infection that requires treatment, so it is not a "problem" in the classical sense. However, it can be a source of concern for parents.
**Option B:** Transitional stools are not a disease or a problem in and of themselves, but rather a sign of the transition from meconium to bile-stained stools.
**Option C:** Mongolian spots are not a problem, as they are benign and do not cause any symptoms or discomfort.

**Clinical Pearl / High-Yield Fact**
Neonates often present with a variety of transient conditions that can be confused with disease. A high index of suspicion and a thorough understanding of normal neonatal physiology are essential for accurate diagnosis and management.

**✓ Correct Answer: D. All of the above**