Principle of Radiotherapy is:

Ans: C (DNA damage) Ref: General Principles of Radiation Therapy by Gary J Schreiber, Medscape and Perez and Brady's Principles and Practice of Radiation Oncology, Edited by Edward C. Halperin, 5 Ed, pg 10Explanation:" The exact mechanism of cell death due to radiation is still an area of active investigation. A large body of evidence supports double- stranded breaks of nuclear DNA as the most important cellular effect of radiation. This breakage leads to irreversible loss of the reproductive integrity of the cell and eventual cell deathRef: MedscapeThe biologic effect of ionizing radiation are largely the result of DNA damage, which is caused directly by ionization within the DNA molecule or indirectly from the action of chemical radicals formed as a result of local inoizations in water.The general forms of DNA damage are:A) Base damage DNA protein cross linking Single strand breaksD) Double strand breaksE) Complex combination of all these