. Although the population of a certain salmon species in the Pleasant River % \) p0 R7 K6 ]5 \
has not decreased in the last five years, the average size of adult female
: x7 R: x5 b# _# M7 a6 T. Esalmon of that species in the river has decreased significantly in this time.
0 u: L" ?1 Y, o, z6 _The latter fact indicates that the population of this species is ultimately
8 @4 r% w) x& ^; C! M% G! [endangered, since small fish of a given species lay far fewer eggs than
3 j# @. f6 t* Edo large fish of the same species.; \: E* I/ w* z% n. o
Which of the following is an assumption on which the argument depends?
, ?! l8 F: J4 ?" i( H A Excluding fish of the salmon species, the average size of fish in the
: J# D1 v% x" F Pleasant River has increased over the past five years. 0 c+ `+ J7 V1 v3 W: T: J
B The largest adult female salmon living in the Pleasant River five * o- A+ a7 X% z4 E6 o$ c( B
years ago were significantly larger than the largest adult female
+ s! b K! a: k/ w salmon living there now.
/ y" j1 s& s: O8 i* |6 H7 d- ~ C Smaller salmon are not an easier prey for salmon predators than are $ d, J7 g9 k- d& S; A
larger salmon. 1 _+ \ D7 l; [9 E2 v! S
D The total number of eggs laid each year by salmon of the species ; c( z+ b6 U, ]! I
in the Pleasant River has not varied significantly over the past five
4 o) y' l& o! N' b9 o+ K9 K years.
+ ?3 j" r4 \, ^7 i2 P8 X8 S! \0 }/ I: i E The proportion of the eggs laid by small salmon of the species that 1 C5 w8 o0 T$ S; W) L
hatch into fish that reach reproductive maturity is not significantly * b# D7 o0 n) ~8 I9 K
greater than that of the eggs laid by large salmon of the species.
! C. W$ Z C& \4 _; o q$ D答案E |