Step 1: Understanding the Concept
Protein-energy malnutrition has two main forms. One is caused mainly by lack of protein, the other by lack of both protein and calories.
Step 2: Match the symptoms
A protruding belly and swelling (oedema) of the lower legs occur because low blood protein lets fluid leak into tissues.
Step 3: Compare the options
Marasmus shows severe wasting without oedema. Jaundice affects the liver and malaria is caused by a parasite, so neither is a nutritional deficiency disease.
Step 4: Conclusion
The protein-deficiency disease with a swollen belly and leg oedema is kwashiorkor.
Final Answer:
The disease is kwashiorkor.
\[ \boxed{\text{(A) }\text{Kwashiorkor}} \]