Introduced in 1698, the term "conscious" acquired at least five differ

Official Explanation :

The answer choices contain a variety of tests for the verb fade, indicating that the question tests the correct form of that verb.

Choice A is incorrect because when a sentence describes two completed actions in the past, the past perfect (had not faded) is used to refer to the action that came first. In this case, the action in question must have come second, as indicated by the phrase in more recent times.

Choice B is incorrect because of which must refer to the noun that immediately precedes it (50 years), and it does not make any sense to say that the ambiguity of 50 years has not faded. Clearly, it is the ambiguity of the term "conscious" that has not faded.

Choice C is correct because it uses the simple past to refer to the first action (the term "conscious's" acquisition of at least five definitions); that first action occurred firmly in the past. The use of the present perfect to refer to the second action (the ambiguity of the term "conscious" not fading) is also logical, indicating that the action is continuing into the present.

Choice D is incorrect because the plural pronoun their disagrees with its referent, the singular noun the term. The only plural noun is 50 years, and logically, the pronoun in question cannot refer to it.

Choice E is incorrect because its ambiguity not fading should be its ambiguity has not faded; the gerund is awkward and less precise than the present perfect.