Information: - A proton is a subatomic particle, symbol or , with a positive electric charge of +1"e" elementary charge and mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons". One or more protons are present in the nucleus of every atom. They are a necessary part of the nucleus. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol Z). Since each element has a unique number of protons, each element has its own unique atomic number. The word "proton" is Greek for "first", and this name was given to the hydrogen nucleus by Ernest Rutherford in 1920. In previous years, Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by atomic collisions. Protons were therefore a candidate to be a fundamental particle, and hence a building block of nitrogen and all other heavier atomic nuclei. - The neutron is a subatomic particle, symbol or , with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons, each with mass approximately one atomic mass unit, constitute the nucleus of an atom, and they are collectively referred to as nucleons. Their properties and interactions are described by nuclear physics. - Angina pectoris, commonly known as angina, is the sensation of chest pain, pressure, or squeezing, often due to not enough blood flow to the heart muscle as a result of obstruction or spasm of the coronary arteries. While angina pectoris can occur due to anemia, abnormal heart rhythms and heart failure, its main cause is coronary artery disease, an atherosclerotic process affecting the arteries feeding the heart. The term derives from the Latin "angere" ("to strangle") and "pectus" ("chest"), and can therefore be translated as "a strangling feeling in the chest". - Tritium (or ; symbol ' or ', also known as hydrogen-3) is a radioactive isotope of hydrogen. The nucleus of tritium (sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of protium (by far the most abundant hydrogen isotope) contains one proton and no neutrons. Naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays. It is produced by irradiating lithium metal in a nuclear reactor. Tritium is used as a radioactive tracer, in radioluminescent light sources for watches and instruments, and in nuclear weapons. The name of this isotope is formed from the Greek word ("tritos") meaning "third". - A radioactive tracer, or radioactive label, is a chemical compound in which one or more atoms have been replaced by a radioisotope so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products. Radiolabeling is thus the radioactive form of isotopic labeling. - Lithium (from , "stone") is a chemical element with the symbol Li and atomic number3. It is a soft, silver-white metal belonging to the alkali metal group of chemical elements. Under standard conditions, it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable. For this reason, it is typically stored in mineral oil. When cut open, it exhibits a metallic luster, but contact with moist air corrodes the surface quickly to a dull silvery gray, then black tarnish. Because of its high reactivity, lithium never occurs freely in nature, and instead, appears only in compounds, which are usually ionic. Lithium occurs in a number of pegmatitic minerals, but due to its solubility as an ion, is present in ocean water and is commonly obtained from brines and clays. On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride and potassium chloride. - AstraZeneca plc is a BritishSwedish multinational pharmaceutical and biopharmaceutical company. In 2013 it moved its headquarters to Cambridge, England, and concentrated its R&D in three sites: Cambridge, Gaithersburg, Maryland (location of MedImmune) for work on biopharmaceuticals, and Molndal (near Gothenburg) in Sweden, for research on traditional chemical drugs. In 2015 it was the eighth largest drug company in the world based on sales revenue. - Alprenolol, or alfeprol, alpheprol, and alprenololum (Gubernal, Regletin, Yobir, Apllobal, Aptine, Aptol Duriles), is a non-selective beta blocker as well as 5-HT receptor antagonist, used in the treatment of angina pectoris. It is no longer marketed by AstraZeneca, but may still be available from other pharmaceutical companies or generically. - A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in propulsion of ships. Heat from nuclear fission is passed to a working fluid (water or gas), which runs through steam turbines. These either drive a ship's propellers or turn electrical generators. Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use, or for production of weapons-grade plutonium. Some are run only for research. Today there are about 450 nuclear power reactors that are used to generate electricity in about 30 countries around the world. - Dihydroalprenolol ( DHA ) is a hydrogenated alprenolol derivative that acts as a beta - adrenergic blocker . When the extra hydrogen atoms are tritium , it is a radiolabeled form of alprenolol , which is used to label beta - adrenergic receptors for isolation . - Cosmic rays are high-energy radiation, mainly originating outside the Solar System. Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary particles that sometimes reach the surface. Composed primarily of high-energy protons and atomic nuclei, they are of mysterious origin. Data from the "Fermi" space telescope (2013) have been interpreted as evidence that a significant fraction of primary cosmic rays originate from the supernovae explosions of stars. Active galactic nuclei probably also produce cosmic rays. - Beta blocker, also written -blocker, is a class of medications that are particularly used to manage cardiac arrhythmias, and to protect the heart from a second heart attack (myocardial infarction) after a first heart attack (secondary prevention). They are also widely used to treat hypertension, although they are no longer the first choice for initial treatment of most patients. - Hydrogen is a chemical element with chemical symbolH and atomic number1. With an atomic weight of , hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed "protium" (name rarely used, symbol H), has one proton and no neutrons. - A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion (thermonuclear weapon). Both reactions release vast quantities of energy from relatively small amounts of matter. The first test of a fission ("atomic") bomb released the same amount of energy as approximately . The first thermonuclear ("hydrogen") bomb test released the same amount of energy as approximately . After reading the paragraphs above, we are interested in knowing the entity with which 'dihydroalprenolol' exhibits the relationship of 'instance of'. Find the answer from the choices below. Choices: - alkali - antagonist - atmosphere - atomic pile - beta blocker - biopharmaceutical - building - candidate - cause - chemical compound - chemical element - chest - chloride - class - company - cut - data - device - district - energy - england - fluid - force - gas - generation - group - hydrogen - industrial process - isotope of hydrogen - label - matter - may - metal - name - nuclear reactor - nucleus - number - ocean - oil - particle - physics - process - radioactive tracer - release - research - space - standard - stone - surface - symbol - term - test - thermonuclear weapon - three - treatment - two - virtue - weapon - work
A:
chemical compound