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17. Although the population of a certain salmon species in the Pleasant River
has not decreased in the last five years, the average size of adult female
salmon of that species in the river has decreased significantly in this time.
The latter fact indicates that the population of this species is ultimately
endangered, since small fish of a given species lay far fewer eggs than
do large fish of the same species.

Which of the following is an assumption on which the argument depends?

   A  Excluding fish of the salmon species, the average size of fish in the
   Pleasant River has increased over the past five years.
   B  The largest adult female salmon living in the Pleasant River five
   years ago were significantly larger than the largest adult female
   salmon living there now.
   C Smaller salmon are not an easier prey for salmon predators than are
   larger salmon.
   D The total number of eggs laid each year by salmon of the species
   in the Pleasant River has not varied significantly over the past five
   years.
   E The proportion of the eggs laid by small salmon of the species that
   hatch into fish that reach reproductive maturity is not significantly
   greater than that of the eggs laid by large salmon of the species.