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: Dental
Activity of all disinfectants is: 
Select and explain. 
A. Reduced by organic debris or blood, B. Increased with heat, C. Hastened by adding 5% oxygen, D. Nullified by ethylene dioxide gas
A: Reduced by organic debris or blood
Answer: A: Reduced by organic debris or blood 
Explanation: None