400
Replace the portion in the parentheses with one of the following answer choices:
Many of the instruments used in early operations of the United States Army Signal (Corps were adaptations of equipment used by the Plains Indians, particularly that of the heliograph).
(A) Corps were adaptations of equipment used by the Plains Indians, particularly that of the heliograph
(B) Corps, there were adaptations of equipment used by the Plains Indians, particularly the heliograph
(C) Corps, and in particular the heliograph, was an adaptation of equipment used by the Plains Indians
(D) Corps, and in particular the heliograph, were adaptations of equipment used by the Plains Indians
(E) Corps being adaptations, the heliograph in particular, of those used by Plains Indians
(D) Corps, and in particular the heliograph, were adaptations of equipment used by the Plains Indians