I want to know the answer to the following question:
How many persons were still unaccounted for in Yingxiu?
All the background I'm provided with is that "At the start of rescue operations on May 12, 20 helicopters were deployed for the delivery of food, water, and emergency aid, and also the evacuation of the injured and reconnaissance of quake-stricken areas.". Is that enough to answer the question?
Answer: no