The correct answer is B. 's
Explanation:
In the English language, one of the most common ways to express a noun owns something is by using the apostrophe. However, this follows strict rules, indeed in the case of singular nouns that do not end in "s" the possessive is formed by adding the apostrophe followed by an "s" or 's, for example in Maria's house. On the other hand, if the singular noun already ends in "s" only the apostrophe is added as in Charles' house. In the case of plural nouns, similar rules apply as if the noun does not end in "s" the apostrophe and the "s" need to be added as in children's needs or men's ideas. Therefore, the possessive of plural nouns that do not end in s are formed by adding 's.
Answer:
the author outlines events chronologically to give a complete account of the United States entering world war 1
