Originally Answered: To preserve natural resources, which of the following should be recycled?
Coal, oil, food, and natural gas cannot be recycled in the conventional sense. I suppose carbon dioxide produced from burning coal and oil can be recycled and converted to methanol. Food waste and human and animal waste (the product of food) can be composted. Natural gas produces carbon dioxide when burnt and that could be converted to methanol and reused. In the conventional sense of recycling none of those choices is actually possible. In the unconventional sense, almost everything is recycled eventually by geologic cycles whether we make any effort or not. Nature has been recycling for about 14 billion years now.
Oil spills do contribute to increased global temperatures in the strict sense because most of the oil evaporates and is broken down by photochemical reactions in the atmosphere to carbon dioxide and water vapor, both of which are greenhouse gases. There is technically no correct choice for that question. Oh, and oil spills will continue because they are naturally occurring events that have taken place for at least the last 400 million years or so, often catastrophically, but commonly on a daily continual basis.
The third question has three examples that are not recycling: reusing plastic bags or furniture, which is actually repurposing or reusing, not recycling. Buying compact fluorescents is not any sort of recycling or repurposing. It is simply different technology that has its own serious environmental issues and can easily be argued to be much more hazardous than using an incandescent powered by solar, wind, hydropower, or natural gas fired power plants due to the mercury vapor that eventually escapes from the compact fluorescent bulb. Only in the case of coal generated electricity does the mercury become a net gain, and the distribution of the mercury emissions will be much more widely distributed and much more difficult to contain, so it represents a long-term hazard from my point of view. The whole promotion of compact fluorescents is simply a statistical lie based on the false assumption that electricity is produced only from coal and the myth that there are actually ways to prevent the mercury in them from entering the environment. I myself am stocking up on incandescents before they are banned in the US at the end of this year. I don't like mercury in my indoor environment no matter how diluted it becomes after the bulb breaks or leaks- and I've experienced both of these issues already. Hopefully the whole compact fluorescent industry will go the way of 5 1/4 inch floppy disks and whale-oil lanterns in a few years and be replaced by LED's.