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
Following can be used as a yardstick for the  assessment of standards of therapy - 
Select and explain. 
A. Specific death rate, B. Case fatality rate, C. Proportional mortality rate, D. Survival rate
D: Survival rate
Answer: D: Survival rate 
Explanation: Survival rate 

It is the proportion of survivors in a group (e.g. of patients) studied and followed over a period of time.
It is a method of describing prognosis in certain disease conditions.
Survival experience can used as a yardstick for the assessment of standard of therapy.
Survival rates have received special attention in cancer studies.

5 years of survival rate = Total no. of patients alive after 5 years / Total no. of patients diagnosed or treated x 100

Survival period is usually reckoned from the date of diagnosis or start of the treatment.