This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Rate limiting step in pyrimidine synthesis ? 
Select and explain. 
A. Dihydro-orotase, B. Ornithine transcarbomoylase, C. Aspaate transcarbomoylase, D. Carbamoyl phosphate synthase-I
C: Aspaate transcarbomoylase
Answer: C: Aspaate transcarbomoylase 
Explanation: Ans. is 'c' i.e., Aspaate transcarbomoylase