D. Composting
Let's take a look at the various options and see if they make sense, given the context of the problem.
A. Biological action
* This option is rather vague and non-specific. It's a possible choice, but if there's something better, then choose it rather than this. Probable wrong choice.
B. Carbon sequestration
* This is the process of storing carbon long term to reduce the amount of CO2 in the atmosphere. Unless Ben has one heck of a lot of organic waste to get rid of, this is a rather silly option and therefore, wrong.
C. Incineration
* The key thing about the problem is "eco-friendly". Incineration will get rid of Ben's leftover food and organic waste, but in doing so will release carbon dioxide into the air and is likely to require some fuel in addition to the organic waste he wants to get rid of. So this too is a bad choice.
D. Composting
* This is the process of breaking down organic matter into compost that can be used as a soil enrichment treatment or fertilizer. The key thing to remember is that the material to be composted has to be organic. Doing this will allow Ben to have compost that he can use in the future on his garden. Overall, this is both an inexpensive and eco-friendly method for Ben to dispose of his leftover food and organic waste.
