**Core Concept**
Physiological jaundice of the newborn is a common condition characterized by a transient increase in bilirubin levels due to the immaturity of the liver and the breakdown of red blood cells. This condition is a normal part of the newborn's adaptation to extrauterine life.

**Why the Correct Answer is Right**
Physiological jaundice typically presents within the first 24 hours of life, but the bilirubin level usually peaks between 3-5 days. The jaundice is caused by the breakdown of red blood cells, which releases unconjugated bilirubin into the bloodstream. The liver is not mature enough to conjugate this bilirubin, leading to an accumulation of unconjugated hyperbilirubinemia. This type of hyperbilirubinemia is always seen in physiological jaundice, as the liver's ability to conjugate bilirubin develops over the first few weeks of life.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because physiological jaundice usually appears within the first 24 hours of life, but the bilirubin level peaks between 3-5 days, not immediately after birth.
**Option B:** This option is incorrect because the jaundice in physiological jaundice is usually limited to the face and upper torso, not the palms and soles, which are characteristic of kernicterus.
**Option C:** This option is incorrect because clinical jaundice in physiological jaundice typically disappears within 1-2 weeks of life, not after 1 month.

**Clinical Pearl / High-Yield Fact**
Physiological jaundice is a self-limiting condition that does not require treatment, but it is essential to monitor the bilirubin level to prevent kernicterus. The American Academy of Pediatrics recommends a bilirubin level of less than 15 mg/dL for infants under 1 month of age.

**✓ Correct Answer: D. It is always unconjugated hyperbilirubinemia**