Please answer this: Extract the answer to the question from the following context. Question: what word is in quotation? Context: Classical statistical mechanics requires the existence of h (but does not define its value). Eventually, following upon Planck's discovery, it was recognized that physical action cannot take on an arbitrary value. Instead, it must be some multiple of a very small quantity, the "quantum of action", now called the Planck constant. Classical physics cannot explain this fact. In many cases, such as for monochromatic light or for atoms, this quantum of action also implies that only certain energy levels are allowed, and values in between are forbidden.
++++++++
Answer: quantum of action

Please answer this: Extract the answer to the question from the following context. Question: What train line is the Northeast Regional? Context: Union Station is further served by four Amtrak lines: the Northeast Regional and the high-speed Acela Express provide service to New York, Washington, D.C. and Boston, and rank as the first and second busiest routes in the country; the New HavenSpringfield Line provides service to Hartford and Springfield, Massachusetts; and the Vermonter provides service to both Washington, D.C., and Vermont, 15 miles (24 km) from the Canadian border. Amtrak also codeshares with United Airlines for travel to any airport serviced by United Airlines, via Newark Airport (EWR) originating from or terminating at Union Station, (IATA: ZVE).
++++++++
Answer: Amtrak

Please answer this: Extract the answer to the question from the following context. Question: How do these changes affect the organism? Context: Instead, he formulated the spearhead model of evolution, a version of genetic pluralism. According to this model, living organisms themselves have goals, and act according to these goals, each guided by a central control. In its most sophisticated form, this is the brain of humans, but controls also exist in much less sophisticated ways for species of lower complexity, such as the amoeba. This control organ plays a special role in evolutionit is the "spearhead of evolution". The goals bring the purpose into the world. Mutations in the genes that determine the structure of the control may then cause drastic changes in behaviour, preferences and goals, without having an impact on the organism's phenotype. Popper postulates that such purely behavioural changes are less likely to be lethal for the organism compared to drastic changes of the phenotype.
++++++++
Answer:
changes in behaviour