Can y’all plzzz help

Of the ones listed here, the factor that had the greatest impact on the eventual destruction of native americans' ways of life was the development of the a) automobile. b) highway. c) railroad. d) steamboat.

Can someone me out here and the tell me the greatest common factor

Drag statements and reasons to each row to show why the slope of the line between d and e is the same as the slope between e and f, given that triangles a and b are similar.