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
Penetration power is more for 
Select and explain. 
A. Hard X-rays, B. Soft X-rays, C. X-rays with long wavelength, D. Grenz rays
A: Hard X-rays
Answer: A: Hard X-rays 
Explanation: None