A student falls asleep as she holds a book containing a portrait of China's late chairman Mao Zedong during a lesson at the Democracy Elementary and Middle School in Sitong town, Henan province December 3, 2013. In a remote part of central China, the day starts at the Democracy Elementary and Middle School with a pre-dawn jog, some revolutionary songs and then an activity long since forgotten at other schools: reciting quotations from Mao Zedong's famed “Little Red Book”. While the ruling Communist Party that Mao led continues to hold him in esteem as the leader of the Communist Revolution, his radical policies and teachings have been largely shelved since his death in 1976 in favour of a pro-market approach that has turned China from a backwater into the world's second biggest economy. The 120th anniversary of Mao's birth is on December 26, 2013. (Photo by Carlos Barria/Reuters)

A truffle is seen on a table in Alba, north-western Italy November 11, 2013. Located in the heart of the Langhe – the hilly southern area of Italy's northwestern Piedmont region – Alba is the country's capital of white truffles, a variety of the prized fungus which grows underground. Truffles are found two to eight inches (5-20cm) below the ground near the roots of trees. They give off an odour which lasts for a limited period of time and can be detected with the assistance of well-trained dogs and experienced hunters. Output of white truffles, which are not cultivated and only grow naturally in forests, has fallen in Italy over the past few years, largely because climate change has brought a damaging mix of drought and torrential rains. (Photo by Stefano Rellandini/Reuters)

“The saguaro (scientific name Carnegiea gigantea) is a large, tree-sized cactus species in the monotypic genus Carnegiea. It is native to the Sonoran Desert in the U.S. state of Arizona, the Mexican state of Sonora, a small part of Baja California in the San Felipe Desert and an extremely small area of California, U.S. The saguaro blossom is the State Wildflower of Arizona”. – Wikipedia

Photo: Daniel Appel (L), a firefighter with Engine 84 from the Lassen National Forest in California and Mike Hallen, (R), Arizona representative of the National Register of Big Trees, measure the circumference of this Saguaro cactus called the "Grand One," in the Tonto National Forest on July 1, 2005 35 miles north of Phoenix, near Carefree, Arizona. The cactus, estimated to be more than 200 years old, measures a circumference of 7 feet, 10 inches (2.4 meters) and stands 46 feet high (14 meters). The cactus was burned in the Cave Creek Complex fire and may not survive. It was once the largest Saguaro in the world, two others have been found recently that have tied it's measurements. The fire has burned more than 214,000 acres of the Sonoran desert. (Photo by Jeff Topping/Getty Images)

A model in Mongolia costumes prepares backstage in Xiangshawan Desert, also called Sounding Sand Desert on July 18, 2013 in Ordos of Inner Mongolia Autonomous Region, China. Xiangshawan is China's famous tourist resort in the desert. It is located along the middle section of Kubuqi Desert on the south tip of Dalate League under Ordos City. Sliding down from the 110-metre-high, 45-degree sand hill, running a course of 200 metres, the sands produce the sound of automobile engines, a natural phenomenon that nobody can explain. (Photo by Feng Li)

People cross a street against strong wind and heavy rainfall under the influence of Typhoon Haiyan, in Sanya, Hainan province November 10, 2013. One of the most powerful storms ever recorded killed at least 10,000 people in the central Philippines, a senior police official said on Sunday, with huge waves sweeping away entire coastal villages and devastating the region's main city. Despite weakening, the storm is likely to cause heavy rains, flooding, strong winds and mudslides as it makes its way north in the South China Sea. (Photo by Reuters/China Daily)

“Igor Sikorsky (May 25, 1889 – October 26, 1972), born Igor Ivanovich Sikorsky was a Russian American pioneer of aviation in both helicopters and fixed-wing aircraft. He designed and flew the world's first multi-engine fixed-wing aircraft, the Russky Vityaz in 1913, and the first airliner, Ilya Muromets, in 1914. After immigrating to the United States in 1919, Sikorsky founded the Sikorsky Aircraft Corporation in 1923, and developed the first of Pan American Airways' ocean-conquering flying boats in the 1930s. In 1939 Sikorsky designed and flew the Vought-Sikorsky VS-300, the first viable American helicopter, which pioneered the rotor configuration used by most helicopters today. Sikorsky would modify the design into the Sikorsky R-4, which became the world's first mass-produced helicopter in 1942”. – Wikipedia

Photo: Westland Sikorsky H-5's, used by British European Airways Helicopters, which fly between London and Birmingham. The Sikorsky H-5, (aka R-5, S-51, HO3S-1, or Horse) (R-5 until 1948; company designation VS-327) is a helicopter built by Sikorsky Aircraft Corporation, formerly used by the United States Air Force, and its predecessor, the United States Army Air Forces, as well as the United States Navy and United States Coast Guard (with the designations HO2S and HO3S). (Photo by Harrison /Topical Press Agency/Getty Images). 22nd May 1951

Faruk, 17, a Rohingya refugee trader holds betel leaves which are on sale at a stall in Palong Khali refugee camp near Cox's Bazar, Bangladesh, November 3, 2017. He left his village in Myanmar when the military opened fire towards the Rohingya. “I buy this betel leaf from Palong Khali market, in one bundle there are 160 pieces, I buy it for 80 taka and I sell it for 100 taka (1 Bangladeshi Taka = 0.012 US Dollar). Bangladeshi's and I sell for the same rate in the camp. Outside in the local market it is 80 taka per bundle. My problem is that I don't have money so I can't buy anything to eat, I can't buy fish to eat”, he said. (Photo by Hannah McKay/Reuters)

A young girl plays on the glass bottom platform of the Oriental Pear TV Tower as she travels with her family on the second day of the Chinese Lunar New Year holiday, also known as Spring Festival, in Shanghai, China on February 18, 2018. Some 287 million tourists travelled in China during the first four days of the week-long Chinese Lunar New Year holiday, up 11.1 percent from the same period last year, new data showed Sunday. (Photo by Imaginechina/Rex Features/Shutterstock)