**Core Concept**
Identical twins, also known as monozygotic twins, are formed when a single fertilized egg splits and develops into two separate embryos. Despite their identical genetic makeup, they can be distinguished from one another through various unique characteristics.

**Why the Correct Answer is Right**
Fingerprints are unique to each individual, including identical twins, due to the random patterns of ridges and valleys formed during fetal development. This uniqueness is a result of the interaction between the embryo's skin and the amniotic fluid, which creates a distinct pattern of fingerprints. In the case of identical twins, their fingerprints are identical at birth but begin to diverge as they develop and grow, making them a reliable method for differentiation.

**Why Each Wrong Option is Incorrect**
**Option B:** DNA fingerprinting, also known as genetic fingerprinting, is a technique used to identify individuals based on their unique DNA patterns. However, identical twins share the same DNA, making DNA fingerprinting unreliable for differentiating them.

**Option C:** Blood grouping involves categorizing blood into different types based on the presence or absence of specific antigens on the surface of red blood cells. While blood grouping can distinguish between individuals, it may not be sufficient to differentiate identical twins, as they often have the same blood type.

**Option D:** Age is not a reliable method for differentiating identical twins, as they are born at the same time and are likely to have the same physical and developmental characteristics.

**Clinical Pearl / High-Yield Fact**
A useful mnemonic to remember the unique characteristics of identical twins is "Fingerprints are Forever Different" (FFFD), which highlights the importance of fingerprints in distinguishing between identical twins.

**✓ Correct Answer: A. Finger print Fingerprints are unique to each individual, including identical twins, due to the random patterns of ridges and valleys formed during fetal development.**