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: Social & Preventive Medicine
All of the following are features of Cross-Over studies except - 
Select and explain. 
A. All patients receive the new therapy, B. Not suitable if drug on interest cures the disease, C. Not suitable if drug is effective only during a certain stage of disease, D. Not suitable if disease does not changes radically during the study
D: Not suitable if disease does not changes radically during the study
Answer: D: Not suitable if disease does not changes radically during the study 
Explanation: None