This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urea Cycle and Disorders, Subject name: Biochemistry
Urea cycle is linked to TCA cycle by - 
Select and explain. 
A. Arginine, B. Ornithine, C. Oxaloacetate, D. Fumarate
D: Fumarate
Answer: D: Fumarate 
Explanation: Ans. is 'd' i.e., Fumarate |Ref: Harper 29th/e p. 276-277]o Fumarate is released during urea cycle, which is an intermediate of Kreb's cycle, thus linking the two.Both urea cycle and TCA cycle have been explained in previous years.