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: Radiology
A patient with cancer received extreme degree of radiation toxicity. Further history revealed that the dose adjustment of a particular drug was missed during the course of radiotherapy. Which of the following drugs required a dose adjustment in that patient during radiotherapy in order to prevent radiation toxicity – 
Select and explain. 
A. Vincristine, B. Dactinomycin, C. Cyclophosphamide, D. 6 – Mercaptopurine
B: Dactinomycin
Answer: B: Dactinomycin 
Explanation: Actinomycin - D (Dactinomycin) is well is well known radiosensitizer. So its dose should be reduced during radiotherapy to prevent radiation toxicity.