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About a century ago, the Swedish physical scientist Arrhenius proposed a law of classical chemistry that relates chemical reaction rate to temperature. According to the Arrhenius equation, chemical reaction are increasingly unlikely to occur as temperatures approach absolute zero,and at absolute zero (zero degrees Kelvin, or minus 273 degrees Celsius) reactions stop. However, recent experi- mental evidence reveals that although the Arrhenius equation is generally accurate in describing the kind of chemical reaction that occurs at relatively high temperatures, at tem- peratures closer to zero a quantum- mechanical effect known as tunneling comes into play; this effect accounts for chemical reactions that are forbidden by the principles of classi- cal chemistry. Specifically, entire molecules can "tunnel" )through the barriers of repulsive forces from other mole- cules and chemically react even though these molecules do not have sufficient energy, according to classical chemistry, to overcome the repulsive barrier. The rate of any chemical reaction, regardless of the tem-perature at which it takes place, usually depends on a very important characteristic known as its activation energy. Any molecule can be imagined to reside at the bottom of a so- called potential well of energy. A chemical reaction corre- sponds to the transition of a molecule from the bottom of one potential well to the bottom of another. In classical chemistry, such a transition can be accomplished only by going over the potential barrier between the wells, the height of which remains constant and is called the activation energy of the reaction. In tunneling, the reacting mole-cules tunnel from the bottom of one to the bottom of another well without having to rise over the barrier between the two wells. Recently researchers have developed the concept of tunneling temperature: the temperature below which tunneling transitions greatly outnumber Arrhenius transi ions, and classical mechanics gives way to its quantum counterpart. This tunneling phenomenon at very low temperatures suggested my hypothesis about a cold prehistory of life: the formation of rather complex organic molecules in the deep cold of outer space, where temperatures usually reach only a few degrees Kelvin. Cosmic rays (high-energy protons and other particles) might trigger the synthesis of simple molecules, such as interstellar formaldehyde, in dark clouds of interstellar dust. Afterward complex organic molecules would be formed, slowly but surely, by means of tunneling. After I offered my hypothesis, Hoyle and Wickramasinghe argued that molecules of interstellar form- aldehyde have indeed evolved into stable polysaccharides such as cellulose and starch. Their conclusions, although strongly disputed, have generated excitement among investigators such as myself who are proposing that the galactic clouds are the places where the prebiological evolution of compounds necessary to life occurred.

The author of the passage is primarily concerned with

According to the passage, classical chemical reactions and tunneling reactions are alike in which of the following ways?

According to the Arrhenius equation as discussed in the passage, which of the following statements about chemical reactions is true?

The author's attitude toward the theory of a cold pre- history of life can best be described as

The author's hypothesis concerning be cold prehistory of life would be most weakened if which of the following were true?

Which of the following best describes the hypothesis of Hoyle and Wickramasinghe as it is presented in the passage?

Which of the following best describes the organization of the first two paragraphs of the passage?