This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Storage of vaccines, Subject name: Pediatrics
The shake test shown below can be done to know: 
Select and explain. 
A. Whether vaccine was exposed to heat, B. Whether vaccine had been frozen at some point of time in the cold chain, C. Whether expiry date of vaccine has reached, D. Whether the vaccine needs to be mixed with normal saline
B: Whether vaccine had been frozen at some point of time in the cold chain
Answer: B: Whether vaccine had been frozen at some point of time in the cold chain 
Explanation: Shake test: - Test done to check cold damage to Vaccine due to freezing. - Once the vaccine is frozen, it tends to form flakes which gradually settle to the bottom, after the l is shaken. - Thus, sedimentation occurs faster in a vaccine l which has been frozen as compared to control l. - These ls should be discarded irrespective of their expiry date. - Used for DPT, DT, TT or Hepatitis B