Clay "caganers" representing Spanish Prime Minister Mariano Rajoy (2nd L), Podemos's candidate Pablo Iglesias (R), Socialist Party (PSOE) leader Pedro Sanchez (2nd R) and Ciudadanos party leader Albert Rivera (L) are seen on display at the Santa Llucia Christmas market in central Barcelona, Spain, December 16, 2015. Catalans hide “caganers” or defecators, in Christmas Nativity scenes to let friends hunt for them during Christmas celebrations. The “caganers”, which symbolise defecation and fertilization of the earth, are believed to bring prosperity and luck for the coming year. (Photo by Albert Gea/Reuters)

Soldiers of China's People's Liberation Army (PLA) jump as part of their winter training in temperature of negative 26 degrees Celsius at China's border with Russia in Heihe, Heilongjiang province, December 14, 2015. (Photo by Reuters/Stringer)

Droid BB-8 arrives at the world premiere of the film “Star Wars: The Force Awakens” in Hollywood, California, December 14, 2015. (Photo by Mario Anzuoni/Reuters)

A man rides his loaded tricycle next to three schoolgirls in Shanghai on December 11, 2015. (Photo by Johannes Eisele/AFP Photo)

A Hypsiboas crepitans frog is pictured at a terrarium in Caracas November 30, 2015. Venezuelan frogs and toads are in critical danger due to climate change as rising temperatures complicate reproduction and spread a deadly fungus, say scientists, who liken the species to canaries in a coalmine warning of imminent danger. The survival of a group of nearly 20 frog and toad species, which top Venezuela's list of endangered species, may rest on a small group of academics in a Caracas laboratory attempting to recreate the amphibians' natural reproductive conditions. (Photo by Carlos Garcia Rawlins/Reuters)

Star Wars collector James Burns, 44, poses for a photograph with some of his collection in London December 2, 2015. He said “I've met so many wonderful people, all over the world. It's a wonderful community of likeminded people with an interest in Star Wars. There's nothing else like it”. (Photo by Paul Hackett/Reuters)

A child dressed in an imitation dress of army soldier enjoys a cold drink during a religious procession in Amritsar, India, 15 December 2015. The religious procession was taken out on the eve of the martyrdom day of the 9th Guru or Master of the Sikhs Sri Guru Tegh Bahadur Ji. Guru Tegh Bahadur was executed for not converting to Islam on the orders of Mughal Emperor Aurangzeb in Delhi in 1675 AD. The place of this occurrence is called Gurudwara Sis Ganj at Delhi. Guru Tegh Bahadur the youngest of the five sons of Guru Hargobind was born in Amritsar in 1621. (Photo by Raminder Pal Singh/EPA)

An ice covered entrance door to the international gene bank Svalbard Global Seed Vault (SGSV) near Longyearbyen on Spitsbergen, Norway, October 20, 2015. Two consignments of crop seeds will be deposited next year in a “doomsday vault” built in an Arctic mountainside to safeguard global supplies. The vault, which opened on the Svalbard archipelago in 2008, is designed to protect crop seeds, such as beans, rice and wheat against the worst cataclysms of nuclear war or disease. (Photo by Anna Filipova/Reuters)