单选题 A certain species of bird has two basic varieties, crested and noncrested. The birds, which generally live in flocks that contain only crested or only noncrested birds, tend to select mates of the same variety as themselves. However, if a bird that is raised in a flock in which all other members are crested is later moved to a mixed flock, then that bird—whether crested or noncrested—is likely to select a crested mate. This fact indicates that the birds' preference for crested or noncrested mates is learned rather than genetically determined. Which one of the following, if true, provides the most support for the argument?

A、 Birds of other species also tend to show preferences for mates that have one or another specific physical feature.
B、 In general there are few behavioral differences between the crested and noncrested birds of the species.
C、 Both the crested and noncrested birds of the species tend to select mates that are similar to themselves in size and age.
D、 If a crested bird of the species is raised in captivity apart form other birds and is later moved to a mixed flock, that bird is likely to select a crested mate.
E、 (E) If a bird of the species is raised in a flock that contains both crested and noncrested birds, that bird shows no preference for one variety or the other in its selection of a mate.

【正确答案】 E

【答案解析】[解析] 要决定一只乌在选择配偶时的行为是由遗传决定的，还是后天习得的，就要看它们生活的环境对他们选择配偶有多大的影响。(E)表明了一只生活在由两种变种组成的乌群中的鸟在选择配偶时不会对某一个变种的鸟有所偏好就表明了是这只鸟生活的环境而不是它的遗传特性决定它在择偶时的行为，所以(E)能对本题的结论形成最有力的支持；(D)反对本题的结论；(A)、(B)和(C)均为无关选项。