Which statement is wrong about "single channel" recognition system and "multi-channel" recognition system?
A.
"Single channel" recognition system is designed to be used at the entrances to buildings.
B.
Multi-channel system can identify individuals in a crowd of up to 50 people within 3 seconds.
C.
"Multi-channel" recognition system uses groups of surveillance cameras.
D.
They are two of the main products sold by Hanwang.