单选题
8. Spiders of many species change color to resemble the color of the flowers they sit on. Many animals that prey on such spiders possess color discrimination so acute that they, unlike human beings, can readily see the spiders despite the seeming camouflage. It is unlikely, therefore, that the spiders' color changes confer significant survival benefit on these spiders.
Which of the following would it be most useful to determine in order to evaluate the argument? ______