I believe it would be -ous.
B. Readability and accuracy are two most important elements for an ideal translation.
Readability refers to the fact that the translation "flows" - it sounds natural and there are no problems reading this text. Accuracy refers to the fact that the words are translated correctly.
The answer is d, it introduced the quote, quoted the quote, correctly cited the author and page number, then explained why the quote was important.
