You are correct!  The answer is "d.  As much or as little time as I want."

You can compost most items with very little effort. Only large volumes of "green" material will require more intense effort during the initial stages. But as with many activities, the more that you put into it the more you get out of it. So the amount of time it takes to make compost is as variable. Just remember that any effort you make to compost will go a long way to reducing pressure on our landfills, and adding organic matter to our highly depleted sub-tropical soils. You can make a difference.