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
Ionising radiation acts on tissue depending upon: 
Select and explain. 
A. Linear acceleration energy, B. Excitation of electron from orbit, C. Formation of pyrimidine dimers, D. Thermal injury
B: Excitation of electron from orbit
Answer: B: Excitation of electron from orbit 
Explanation: Ans. Excitation of electron from orbit