The correct answer is A. sugarcane.
Ethanol is a biofuel that can be produced from a variety of plant materials, including sugarcane, corn, and switchgrass. Sugarcane is a particularly good source of ethanol because it is a fast-growing crop that can be harvested year-round. Ethanol is a renewable energy source that can help to reduce our reliance on fossil fuels. It is also a cleaner-burning fuel that can help to improve air quality.
Potatoes, rice, and wheat are also potential sources of ethanol, but they are not as efficient as sugarcane. Potatoes and rice are starchy crops that require a lot of energy to process into ethanol. Wheat is a cereal crop that is not as well-suited for ethanol production as other grains.
In conclusion, sugarcane is the best source of ethanol because it is a fast-growing crop that is efficient to process into ethanol. It is also a renewable energy source that can help to reduce our reliance on fossil fuels.