This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunization, Subject name: Pediatrics
An OPV vial shows this symbol on it. What does it indicate? 
Select and explain. 
A. The vaccine has reached its expiry date, B. The vaccine has not been stored properly, C. The vaccine vial is empty, D. Use the vaccine if expiry date not reached
D: Use the vaccine if expiry date not reached
Answer: D: Use the vaccine if expiry date not reached 
Explanation: d. Use the vaccine if expiry date not reachedThis is a vaccine vial monitor (VVM) showing white inner square & blue outer circle; VVM provides an indication of the cumulative heat to which the vial has been exposed