TASK DEFINITION: This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
PROBLEM: Passage: Multiracial Americans are Americans who have mixed ancestry of "two or more races". The term may also include Americans of mixed-race ancestry who self-identify with just one group culturally and socially (cf. the one-drop rule). In the 2010 US census, approximately 9 million individuals, or 2.9% of the population, self-identified as multiracial. There is evidence that an accounting by genetic ancestry would produce a higher number, but people live according to social and cultural identities, not DNA. Historical reasons, including slavery creating a racial caste and the European-American suppression of Native Americans, often led people to identify or be classified by only one ethnicity, generally that of the culture in which they were raised. Prior to the mid-20th century, many people hid their multiracial heritage because of racial discrimination against minorities. While many Americans may be biologically multiracial, they often do not know it or do not identify so culturally, any more than they maintain all the differing traditions of a variety of national ancestries. Question: Why did muticultural Americans hid their heritage?

SOLUTION: many people hid their multiracial heritage because of racial discrimination against minorities

PROBLEM: Passage: Switzerland is one of the richest and wealthiest countries in the world. Switzerland ranks top or close to the top in several metrics of national performance, including government transparency, civil liberties, quality of life, economic competitiveness, and human development. It has the highest nominal wealth (financial and non-financial assets) per adult in the world according to Credit Suisse and the eighth-highest per capita gross domestic product on the IMF list. Zürich and Geneva have each been ranked among the top cities with the highest quality of life in the world, with the former ranked 2nd globally, according to Mercer. Question: What is Switzerland's ranking for per capita gross domestic product on the IMF list?

SOLUTION: eighth-highest

PROBLEM: Passage: Richard Phillips Feynman (/ˈfaɪnmən/; May 11, 1918 – February 15, 1988) was an American theoretical physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics for which he proposed the parton model. For his contributions to the development of quantum electrodynamics, Feynman, jointly with Julian Schwinger and Sin-Itiro Tomonaga, received the Nobel Prize in Physics in 1965. He developed a widely used pictorial representation scheme for the mathematical expressions governing the behavior of subatomic particles, which later became known as Feynman diagrams. During his lifetime, Feynman became one of the best-known scientists in the world. In a 1999 poll of 130 leading physicists worldwide by the British journal Physics World he was ranked as one of the ten greatest physicists of all time. Question: Feynman proposed a integral model in particle physics, what was it?

SOLUTION:
parton model