36套exe7一道题的疑问

gjxwinUID: 3457128

晚上做了下36套exe7，其中第11题很是不解，，答案选的是BC，可是个人感觉A是对的啊，应该选ABC，第二段的开头明明说到了the variation is adaptive, a responsive to environment differences.求解答，谢谢！

yiruskyUID: 3408934

虽然文章之前虽有提到不同环境，但是最后一段反驳了这个观点。Line 45 "biologists concluded that there is no important adaptive difference between left- eyedness and right-eyedness..." ,difference对应variation。 我是这样子理解的。