Which statement best explains how the organizational structure of the passage helps develop the main idea? Help!

Does anyone know the answer to the question?

Which part of the original work should the adaptation retain

Which choice is a major detail from paragraph two? a) the great wall is a large network of several walls and towers. b) the great wall looks like a long wall snaking its way across china. c) the great wall was constructed over hundreds of years beginning in 221 b.c. d) the great wall construction encouraged several independent kingdoms to unite.