In the past three summers, increasing numbers of migratory marine mammals
" q+ F- a4 r/ |4 l# I" \, C have died in the Gordon City Bay area. It is now hypothesized that certain clean -2 y3 k1 r5 {5 h, h4 G) a7 J
ing products for ships' hulls which contain the chemical LSA are responsible for
2 D( ?& n5 C3 g: i k the deaths. LSA, which weakens mammals' defenses against infections, has " k/ T% Q/ J5 H" g
been found in tissue samples from many of the dead animals and, significantly,
, i. g+ k( ]" m3 @& y& M4 ^& ] the animals died of a viral infection not usually fatal to them.3 |8 H- j" ~' m, ?# h1 l
Which of the following, if true, most strongly supports the hypothesis given?7 M/ [$ M" W6 f; q( G
A The cleaning products containing LSA came onto the market about four ( ^& \$ p8 v0 p" u6 W) Y
years ago and have, because of their superior effectiveness in cleaning $ h, `" t4 h, q
ships' hulls, displaced the cleaners previously used.
* N6 O7 Q1 r; \5 h- R% P B Tissue samples from the dead marine mammals have also been found to 8 P3 O! C4 F. `. b. I4 s
contain many substances other than LSA that are toxic to marine mammals.
% @" z! t) \% O# }* ] C There are some indications that the virus that caused the deaths of marine ; E) v8 B' e/ }/ H& T' _
mammals around Gordon City Bay has mutated in recent years into a more# G0 G3 u6 b& J4 _8 |
harmful form.
4 M( F1 J& ~- ]/ C4 k' a Q D Few of the marine mammals summering around Gordon City Bay ever stray
( n4 p* e% V! ~) _ into Gordon City harbor and its extensive seaport facilities. 6 W. P i; H& }4 j) i3 q
E During the past three years in Gordon City Bay, there have been a number + j5 [. ^3 n0 w) o4 l: E3 r; w( N2 _
of fairly large fish kills in addition to increased deaths of marine mammals. 3 m. w. u; e, ^
答案：A |
发表于 2012-8-15 12:40:43
