The increasing use of colloquialisms (slang expressions) is degrading the English language. A phrase such as "she was like, 'No way!', you know?" - a meaningless collection of English words just a few decades ago - is commonly understood today to mean "she was doubtful." No language can have such imprecise word usage without a corresponding decrease in the quality of expression.
The argument relies on which one of the following assumptions?
A. Colloqualisms (slang expressions) always evolve out of a meaningless collection of words.
(A) is incorrect because the source of colloquial or slang expressions is not germane to the argument; the argument concerns their effect on the language, not where they come from or the reasons why they are used. The example provided in the stimulus arose out of "a meaningless collection of words," but even if they come from other sources as well, the claim that they degrade the language is still viable.
B. The slang expressions in common use today make the English language imprecise on a large scale.
(B) is correct. The argument makes a very broad statement with far-reaching implications, based on what appears to be a very small sample. The only way the argument holds water is if this is a large-scale problem; that slang usage is so pervasive that it degrades the language itself, not just the people who speak or write using slang.
C. The Russian, French and German languages do not contain as many colloquialisms as English.
(C) is incorrect because the author makes no attempt to compare English to any other language, let alone these three specific ones, nor indeed to other languages in general. The quantity of colloquialisms in other languages has no bearing on the effect colloquial usage has on English.
D. The English language would not lose any of its quality or precision if there were no alternative, informal way to say "she was doubtful."
(D) is incorrect because the author implies that widespread and insidious use of slang expressions is degrading the language, not this example alone. Even if one could argue that the language would not be degraded if there were no colloquialisms at all, the author is certainly not assuming that this one expression alone degrades the language all by itself, or that the problem could be fixed by limiting this expression to those three words.
E. The widespread use of slang expressions is the worst thing that could possibly happen to the English language.
(E) is incorrect because it's an opinion, and an opinion cannot be an underlying assumption.