I would say that a good candidate is the idea of democracy: from Greece and Rome.
Napoleon's conquest was largely fueled by nationalism, which was a relatively new idea that then took hold of Europe in the 1800s and contributed to late colonial efforts around the world. After Napoleon was defeated, the borders of Europe were redrawn to create a more stable balance of power. These nations shifted to more conservative governments to prevent similar revolutions and rebellion. Importantly,
It can't be A because to actively participate in policy making, you must be engaged in politics yourself.
It can't be B because for there to be communication, there must be talking and hearing, back and forth. The media is one sided.
Although the media does influence policy decisions, it doesn't facilitate that to the public, so it can't be C.
D. The ability to hear discussions on laws and the lawmaking process
This is the correct answer. Because the media is one sided (Information comes, but doesn't go back), but that's all you need if what you want is to be informed about what is going on and you can decide to follow/watch a channel that talks about the specific subject that you are interested in. If that in the case, Lawmaking process can be one of them.