Two dangers of including too many direct quotations from outside sources in your research papers is:
Your paper can jump from topic to topic instead of staying clearly on your main point.
You might unintentionally plagiarize information by not properly citing it.
A direct quotation is a report of the exact same words of an author and are placed inside quotation marks (") in a written work. They differ from the indirect quotation because in those you paraphrase, write with your own words, what the author said.
If you add too many of this quotations you can skip one unintentionally and that would be plagiarism and also you would make the text hard to read because you will go from one citation to another turning your research paper into a list of quotations from others authors. The quotation must be used only to support your own ideas or refute the other author´s ones.
I believe the correct answer is 20th Century: made. "...when those muscles and joints were rendered capable of motion..." is used to mean - when Frankenstein was made, he was given the ability to move. The other options don't really convey the same meaning, so I believe the last option is correct.