<prompt> 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 toxicityVincristineDactinomycinCyclophosphamide6 Mercaptopurine  <response>: Actinomycin - D Dactinomycin is well is well known radiosensitizer. So its dose should be reduced during radiotherapy to prevent radiation toxicity. 