This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Key enzyme in urea synthesis is: \nSelect and explain. \nA. Urease, B. Carbamoyl Synthetase, C. Arginase, D. Ornithine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Carbamoyl SynthetaseCarbamoyl synthetase catalyses the first step in urea cycle or Krebs Henseleit cycle and it is a rate limiting step in urea synthesis.', 'role': 'assistant'}]