What Innovation in Clerical Work Occurred During the United States

What innovation in clerical work occurred during the United States' Civil War?

A) Typewriters were invented.
B) Battlefield logistics planning led to the development of shorthand.
C) A process used to manufacture field artillery shells was adapted to produce carbon paper.
D) The army developed a specialized job of secretary.
E) Because of a shortage of men, women were hired as clerks in the Department of Treasury.