Prolonged and unseasonable frosts produce frost rings in deciduous trees, which grow in moderate climates. Frost rings do not appear in any of the fossilized deciduous trees that have been found in Antarctica. Hence, it is unlikely that such frosts occurred in Antarctica at the time the fossilized trees lived. Which of the following is an assumption on which the argument depends？
A. There are fossilized nondeciduous trees from Antarctica that bear frost rings.
B. Deciduous trees are more likely to bear frost rings than are other tree varieties.
C. The process of fossilization does not completely obscure frost rings in deciduous trees.
D. Present-day deciduous trees are more sensitive to changes in temperature than were the deciduous trees of ancient Antarctica.
E. Prolonged and unseasonable frosts that might have occurred in Antarctica when the now-fossilized trees were still living did not always produce frost rings in deciduous trees.
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In a physical education class, 20 students were tested on archery target shooting. These students were then given a two-day training course in archery technique. The students were tested again and showed a 30 percent increase in accuracy. This result proves that the course was effective in increasing peoples target-shooting accuracy. Which of the following, if true, gives the strongest support to the argument above？
A. The students were all excellent athletes, and excellent athletes tend to be good at target shooting.
B. The first testing session functioned as a practice session for the second testing session.
C. The accuracy with which people can shoot arrows is strongly related to the sharpness of their vision.
D. A similar group of students who were also tested on archery target shooting but were not given the course did not show an increase in accuracy.
Excellence in archery target shooting is an accomplishment achieved by relatively few of the people who take up the sport.
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