Dogs, especially sniffer dogs, have a far better sense of smell than humans because their smell receptors are much longer than those in human noses. human noses differ from person to person, but they can affect the way a person tastes food. sniffer dogs are used by police and security personnel throughout the world to detect drugs in airports and other busy places. they are specially trained and can pick up even the lightest scents of drugs or firearms.

3.
this passage is mostly about

smell receptors.
airport security.
drug sniffing dogs.
human noses.