Help plz very urgent

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.

Icould really use some with this question.

26) -2(7x) = (-2 • 7) x a. associative property of addition b. associative property of multiplication c. commutative property of multiplication d. commutative property of addition