| 6。 A linguist recently argued that all human languages must have a common origin because some concepts are universal; that is, they appear in all languages. For example, all languages are capable of describing lightness and darkness.
Which one of the following, if true, would most seriously weaken the argument?
(A) The Burmese language does not contain basic nouns like automobile and airplane.
(B) No one linguist could possibly speak all known languages.
(C) All speakers, regardless of their languages, are confronted with similar stimuli like lightness and darkness.
(D) The similarity between human language and dolphin language has not been attributed to a common origin.（C）
(E) Some languages include concepts of which speakers of other languages are not even aware.
答案是C， 问为什么D不对？
C是提供了一个它因解释吗？但我觉得这个它因并不能否定common origin的存在啊？ | 
