This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Targeted Anticancer Drugs and Immunosuppressants, Subject name: Pharmacology
Which of the following monoclonal antibody is used for treatment of colorectal carcinoma? 
Select and explain. 
A. Pembrolizumab, B. Cetuximab, C. Rituximab, D. Natalizumab
B: Cetuximab
Answer: B: Cetuximab 
Explanation: Cetuximab - Colorectal cancer, Head and neck cancer. Rituximab - B cell NHL, CLL Natalizumab - multiple sclerosis Pembrolizumab - head and neck cancer JC virus antibody titre measurement is mandatory during treatment with Natalizumab