CR weaken - baja turtles

[vishalc581]

Loggerhead turtles live and breed in distinct groups, of which some are in the Pacific Ocean and some are in the Atlantic. New evidence suggests that juvenile Pacific loggerheads that feed near the Baja peninsula hatch in Japanese waters 10,000 kilometers away. Ninety-five percent of the DNA samples taken from the Baja turtles match those taken from turtles at the Japanese nesting sites.

Which one of the following, if true, most seriously
weakens the reasoning above?

(A) Nesting sites of loggerhead turtles have been
found off the Pacific coast of North America
several thousand kilometers north of the Baja
peninsula.

(B) The distance between nesting sites and feeding
sites of Atlantic loggerhead turtles is less
than 5,000 kilometers.

(C) Loggerhead hatchlings in Japanese waters have
been declining in number for the last decade
while the number of nesting sites near the
Baja peninsula has remained constant.

(D) Ninety-five percent of the DNA samples taken
from the Baja turtles match those taken from
Atlantic loggerhead turtles.

(E) Commercial aquariums have been successfully
breeding Atlantic loggerheads with Pacific
loggerheads for the last five years.




Can you please explain choices C and D. I didn't get why OA is D and not C.



My reasoning:

Conclusion: " Baja turtles match those taken from turtles at the Japanese nesting sites."

My aim in this question is to weaken the conclusion and "I should see an answer that says BAJA turtles and JAPANESE SITE turtles are different and have DNA SIMILAR TO match those taken from Atlantic loggerhead turtles.

Then I read option C and it says hatchlings in Japanese water have been declining while that of BAJA peninsula is constant. That's why C sounds better than D.


Then, Initially I choose option D because it gives me an alternate reason that BAJA turtles and JAPANESE SITE turtles are different and BAJA turtles DNA

Source: powerscore GMAT CR book.

[RonPurewal]

(C) Loggerhead hatchlings in Japanese waters have
been declining in number for the last decade
while the number of nesting sites near the
Baja peninsula has remained constant.

the red thing does not say that the nesting populations have stayed constant (= the meaning you're mistakenly attributing to it).

[RonPurewal]

...and make sure you understand why choice D is correct.

the pacific and atlantic groups are, factually, separate groups. (they are identified as "distinct groups" in the first sentence; this is a fact, not a hypothesis.)
these groups—which are KNOWN to be separate—share 95 per cent of their genetic material.

this evidence completely defeats any notion that '95 per cent shared genes' might mean 'same population'. it doesn't just weaken the argument—it actually destroys the argument!