The popular notion that a tree's age can be determined by counting the number of internal rings in its trunk is generally true. However, to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often peel away when the temperature exceeds 95 degrees Fahrenheit, leaving the tree with fewer rings than it would otherwise have. So only if the temperature in the Brazilian ash's environment never exceeds 95 degrees Fahrenheit will its rings be a reliable measure of the tree's age.
Which of the following is an assumption on which the argument above depends?
A)The growth of new rings in a tree is not a function of levels of precipitation.
B)Only the Brazilian ash loses rings because of excessive heat.
C)Only one day of temperatures above 95 degrees Fahrenheit is needed to cause the Brazilian ash to lose a ring.
D)The internal rings of all trees are of uniform thickness.
E)The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is not predictable.
I dont know how the answer couldn't be C. From C we get that even when the temperature goes above 95 for one day, a ring is lost. From the original sentence we dont know how long of a period is needed for a ring to decrease nor how many rings decrease per day when the temp is above 95.
I think you have fallen in the trap C. C does say that temperature >95 degree causes
rings lost. But the argument do not
say about the causality, but about the sign that WHEN above 95 degree, the rings lost. You have lured to the disdirection.! The trap made successfully! And count me in sometime!