A linguist recently argued that all human languages must have a common

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. - WRONG. So what there might be many that face similar issues. Besides they still might have some common concepts.

(B) No one linguist could possibly speak all known languages. - WRONG. Irrelevant.

(C) All speakers, regardless of their languages, are confronted with similar stimuli like lightness and darkness. - CORRECT. If all speakers confront similar stimuli then its possible that they might have developed the concepts by themselves.

(D) The similarity between human language and dolphin language has not been attributed to a common origin. - WRONG. Irrelevant.

(E) Some languages include concepts of which speakers of other languages are not even aware. - WRONG. The argument does not say so leaving this end open. However, these languages might still have universal concepts.

IMO Answer C.

(A) is incorrect because automobile and airplane are not universal terms.
(B) is irrelevant.
(C) is the correct answer because if all people are subject to similar stimuli, then one would expect that they would all create words for those stimuli rather than have a common origin.
(D) is irrelevant even though it mixes together common origin with human language.
(E) overstates the claim because the author says that only some--not all—concepts are universal. This is the only incorrect choice with any merit.

FINAL ANSWER IS (C)