3yards is equal less or more than 21 feet

Plz which expression is equivalent to the expression below?

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.

If a || b and b | y, then ? a) x || y. b) x | a. c) a | y. d) a || y.