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
Which amongst the following a marker of carinoma? 
Select and explain. 
A. Cytokeratin, B. Vimentin, C. Calretinin, D. CD45
A: Cytokeratin
Answer: A: Cytokeratin 
Explanation: Cvtokeratins are a class of intermediate filaments that demonstrates epethelial differentiation and are the most commonly used marker to identify 'Carcinomas'.