Input: Article: The top 50 m (160 ft) of a glacier are rigid because they are under low pressure. This upper section is known as the fracture zone and moves mostly as a single unit over the plastically flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in the fracture zone. Crevasses form due to differences in glacier velocity. If two rigid sections of a glacier move at different speeds and directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but in some cases can be 300 m (1,000 ft) or even deeper. Beneath this point, the plasticity of the ice is too great for cracks to form. Intersecting crevasses can create isolated peaks in the ice, called seracs.

Now answer this question: Which zone is the top of the glaciers?

Output: fracture zone

Input: Article: One way of proving that a given disease is "infectious", is to satisfy Koch's postulates (first proposed by Robert Koch), which demands that the infectious agent be identified only in patients and not in healthy controls, and that patients who contract the agent also develop the disease. These postulates were first used in the discovery that Mycobacteria species cause tuberculosis. Koch's postulates can not be applied ethically for many human diseases because they require experimental infection of a healthy individual with a pathogen produced as a pure culture. Often, even clearly infectious diseases do not meet the infectious criteria. For example, Treponema pallidum, the causative spirochete of syphilis, cannot be cultured in vitro - however the organism can be cultured in rabbit testes. It is less clear that a pure culture comes from an animal source serving as host than it is when derived from microbes derived from plate culture. Epidemiology is another important tool used to study disease in a population. For infectious diseases it helps to determine if a disease outbreak is sporadic (occasional occurrence), endemic (regular cases often occurring in a region), epidemic (an unusually high number of cases in a region), or pandemic (a global epidemic).

Now answer this question: What is one way of proving that a given disease is infectious?

Output: satisfy Koch's postulates

Input: Article: At her Silver Jubilee in 1977, the crowds and celebrations were genuinely enthusiastic, but in the 1980s, public criticism of the royal family increased, as the personal and working lives of Elizabeth's children came under media scrutiny. Elizabeth's popularity sank to a low point in the 1990s. Under pressure from public opinion, she began to pay income tax for the first time, and Buckingham Palace was opened to the public. Discontent with the monarchy reached its peak on the death of Diana, Princess of Wales, though Elizabeth's personal popularity and support for the monarchy rebounded after her live television broadcast to the world five days after Diana's death.

Now answer this question: When was Elizabeth's Silver Jubilee?

Output:
1977