In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Ex Input:
What determines the model of forces?, Context: For certain physical scenarios, it is impossible to model forces as being due to gradient of potentials. This is often due to macrophysical considerations that yield forces as arising from a macroscopic statistical average of microstates. For example, friction is caused by the gradients of numerous electrostatic potentials between the atoms, but manifests as a force model that is independent of any macroscale position vector. Nonconservative forces other than friction include other contact forces, tension, compression, and drag. However, for any sufficiently detailed description, all these forces are the results of conservative ones since each of these macroscopic forces are the net results of the gradients of microscopic potentials.

Ex Output:
gradient of potentials


Ex Input:
what is the first area mentioned?, Context: The Monument in the City of London provides views of the surrounding area while commemorating the Great Fire of London, which originated nearby. Marble Arch and Wellington Arch, at the north and south ends of Park Lane respectively, have royal connections, as do the Albert Memorial and Royal Albert Hall in Kensington. Nelson's Column is a nationally recognised monument in Trafalgar Square, one of the focal points of central London. Older buildings are mainly brick built, most commonly the yellow London stock brick or a warm orange-red variety, often decorated with carvings and white plaster mouldings.

Ex Output:
City of London


Ex Input:
How did they become his friends?, Context: Four boarders at his parents' apartments became Chopin's intimates: Tytus Woyciechowski, Jan Nepomucen Białobłocki, Jan Matuszyński and Julian Fontana; the latter two would become part of his Paris milieu. He was friendly with members of Warsaw's young artistic and intellectual world, including Fontana, Józef Bohdan Zaleski and Stefan Witwicki. He was also attracted to the singing student Konstancja Gładkowska. In letters to Woyciechowski, he indicated which of his works, and even which of their passages, were influenced by his fascination with her; his letter of 15 May 1830 revealed that the slow movement (Larghetto) of his Piano Concerto No. 1 (in E minor) was secretly dedicated to her – "It should be like dreaming in beautiful springtime – by moonlight." His final Conservatory report (July 1829) read: "Chopin F., third-year student, exceptional talent, musical genius."

Ex Output:

boarders at his parents' apartments