Pushing on the pedals of a bike cause that bike to move.
Bike commuting truly is green but bike commuting is difficult.
Green commuting can be accomplished through pushing on pedals.
Green what can be accomplished through pushing on pedals?

(a) commuting
(b) Plants growth
(c) walking
(d) driving
(e) Heart rate
(f) running
(g) horse-riding
(h) Movement