What is one way in which parties demonstrate commitment to a platform?

by asking voters for monetary contributions to a campaign fund
by purchasing media advertisements to attack opposing philosophies
by ascertaining that all eligible voters in an area can and will vote
by encouraging and participating in debates over differing ideologies

The correct answer is - by encouraging and participating in debates over differing ideologies.

By using this method of encouraging and participating in public debates over differing ideologies, the parties demonstrate the commitment to their platform, but also in this way they show power and confidence by initiating debates. It is also a method of promotion of their platform to the wider audience and gain political points from it. By standing firm onto their platform and managing to make it sound better than the platform of the opponents they lure the voters onto their side and increase the chances of winning the elections.