What characterized bands such as Joy Division?

For the fire scenes in Humphrey Jennings's feature documentary, Fires Were Started, several bombed-out buildings were set ablaze so that Jennings could set up careful compositions and get enough footage to edit scenes in the style of a fiction film.

Answer the following statement true (T) or false (F)

Retaining some features of a musical idea while changing others is called ________.

A. repetition B. contrast C. variation D. form