The correct answer is C. The tone is too informal and does not use appropriate vocabulary.
Explanation:
An explanatory essay, like any other type of essay, is a formal academic paper in which the author's purpose is to explain some subject guided by a main claim or thesis statement. Similar to other essays the introduction usually includes a hook which is a statement or set of statements used to engage the reader, the presentation of the topic and the thesis statement. Considering all the paper should follow formal and academic conventions, even though if the hook can include rhetorical questions, anecdotes or similar, it is necessary to use a formal tone and appropriate vocabulary. However, in the case of the passage presented in the question the author uses informal tone such as "I know you want to hear more" or "The Neolithic Revolution changed everything in humans" which are too informal and seem something you might include in a conversation but not in a text, also there is an incorrect use of vocabulary in terms of contractions such as "couldn't" or "don't" that is not appropriate. This means the main problem of this passage is that the tone is too informal and does not use appropriate vocabulary.
Nonfiction books are grouped together by subject to make it easier to find a book related to a specific topic. The system that most libraries use to organize books was invented by Melvil Dewey and it is called the Dewey Decimal System. Each book is assigned a three-digit call number based on what the book is about.
The invasions of Germanic groups led to a series of negative changes . Three effects of the Germanic invasions were halt on trade. Transportation of goods became unsafe. Less people were educated, and Europe no longer had one spoken language, unable to be understood by all.
