<span>B. The Readers' Guide is a basic index, while the other resources are full databases allowing access to actual articles.
The Reader's Guide only dates back to 1983 and only contains works that are considered popular. the total number of works within the reader's guide numbers only slightly higher than 450.</span>
For capital letters, we can just add the ending -s, for example:
I got As in the final exam.
for lower-case letters, an apostrophe is used to avoid confusion:
In the multiple-choice exam all the correct answers happened to be a's! (as in: option a)
