Read this excerpt from The Dark Game.

Spies in the Civil War, particularly Confederate spies, relied on courier systems to help speed their information to battlefield generals. Often these courier systems included female operatives. In fact, the Civil War saw an increase in the number of women involved in espionage.

In the rest of the text, how does the author develop this central idea that women were involved in espionage during the Civil War?

A.by stating facts about how many women acted as spies
B.by sharing quotations from women who were spies
C.by discussing the example of a famous woman spy
D.by giving details about how women trained to become spies