Where can birds, puppies, turtles and ants be found together?
If you thought a pet shop, be more creative.
Lin Meizhuo, the security checker at Beijing Capital International Airport, says it would be in passengers' luggage.
The most memorable passenger Lin has met at the security counter of the capital airport's Terminal 2 is a man who hid a tiny bird in his sock.
"He said the bird was a gift for his daughter, and the little bird would not do any harm (to flight safety)," Lin recalled.
The bird was found during the pat-down routine. Smaller than the palm of a hand, the bird looked listless, as if it had been drugged with narcotics, she said.
The bird was later picked up by a friend of the passenger.
Surprisingly, it's not an isolated case. As the country experiences fast economic development and changes in lifestyle, more people are carrying their pets when they travel by air, she said.
But the procedure of shipping animals by air is lengthy and cumbersome. Pets need a number of certificates from animal quarantine departments before being shipped by airlines.
But "people think small animals are harmless, so they would rather try their luck", she said.
Besides birds, a passenger was found carrying a cricket in a box inside his suit, she said.
But most often seen are pets including puppies, turtles and ants carried in cages or boxes, she said.
"But there was once a passenger who tried to take a tiny turtle by hiding it in a napkin package in her bag," she said.
Usually, animals that cannot go with their owners wait behind until the owners can make arrangements for someone to pick them up.
Beijing Capital International Airport transported about 78.7 million passengers last year, the largest number in China.
Security personnel at the airport are now intensifying their efforts to screen out any potential risks after a foiled hijacking in Northwest China.
Six potential hijackers passed through security checks at Hotan airport in the Xinjiang Uygur autonomous region on June 29 and brought metal bars hidden in crutches as well as suspected explosives onto the plane. Fortunately, they were apprehended by passengers and flight workers.
The lesson that the Beijing airport can learn from the incident is that devices are not always reliable, said Tang Hong, an assistant manager at the capital airport's security department.
"It's necessary to master skills that can tell suspicious passengers just by observation," Tang said.
Experts invited from Israel, "the most experienced in the field", just finished training security personnel at the airport last week, she said.
"Ordinary travelers won't look around first and pay special attention to the checking procedure. There will always be signs and hints that can be observed," she said.
But more often, the airport security workers' job is to explain to passengers why they cannot take liquids and lighters on board.
Since 2008, liquids in containers of 100 milliliters or larger, as well as lighters and matches, were forbidden in passengers' carry-on luggage.
"But some passengers still found the rules hard to accept," Lin said.
Lin said that a man who insisted taking toiletries on board once splashed shampoo all over her hair and clothes. In a separate incident, a woman passenger opened one of her six fish cans and splashed the soup onto Lin.
"The job's most challenging part is to stay calm and find solutions for passengers," said Lin, who is a star employee at the airport.
She helped the two passengers check in the toiletries and fish cans, and later received apologies from both.
As for passengers who have a flight to catch and have no time to check in their expensive skincare products or lighters, the airport security department now offers a service to keep goods for passengers for up to 30 days.
"Each day, we get about 70 bottles of expensive skincare products and toiletries, and at least 30 expensive lighters that passengers can't take in carry-on luggage but are not willing to toss away," she said.
At Terminal 2, there is a room full of expensive skincare products and lighters collected from security departments that are stored in 26 cabinets, each 1.8 meters high.
"The cabinets are all full, and we have to put new incoming things on the floor and on the top of cabinets," said Gao Lihuan, an airport employee in charge of the deposited articles.
Gao said some passengers will not come back to pick up their things, and articles that go unclaimed for 30 days will be donated to the Hope Charity Sales Center under the China Youth Development Foundation.
According to the foundation's website, the revenue from charity sales will be donated to public welfare projects.