**Core Concept**
Marasmus and Kwashiorkor are two forms of severe protein-energy malnutrition (PEM) with distinct clinical and biochemical characteristics. Marasmus is characterized by a lack of energy and protein, leading to muscle wasting and a normal serum albumin level. Kwashiorkor, on the other hand, is characterized by edema, muscle wasting, and a low serum albumin level due to inadequate dietary protein.

**Why the Correct Answer is Right**
The correct answer is related to the difference in body composition and biochemical markers between Marasmus and Kwashiorkor. Marasmus is characterized by a depletion of muscle mass and a normal serum albumin level, whereas Kwashiorkor is characterized by edema and a low serum albumin level. The correct answer can be related to the presence or absence of edema, which is a hallmark of Kwashiorkor.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because edema is a characteristic of Kwashiorkor, not Marasmus. Edema in Kwashiorkor is due to hypoalbuminemia and increased capillary permeability.
**Option B:** This option is incorrect because muscle wasting is a characteristic of both Marasmus and Kwashiorkor. Muscle wasting in both conditions is due to inadequate dietary protein and energy.
**Option C:** This option is incorrect because low serum albumin is a characteristic of Kwashiorkor, not Marasmus. Hypoalbuminemia is due to inadequate dietary protein and liver dysfunction in Kwashiorkor.
**Option D:** This option is incorrect because it is a characteristic of both Marasmus and Kwashiorkor. Both conditions are characterized by a loss of body weight and muscle mass.

**Clinical Pearl / High-Yield Fact**
A key difference between Marasmus and Kwashiorkor is the presence of edema, which is a hallmark of Kwashiorkor. Edema in Kwashiorkor is due to hypoalbuminemia and increased capillary permeability.

**Correct Answer: A. Edema is seen in Kwashiorkor and not in Marasmus.**