【单选题】

Which of the following hypothetical discoveries, if made, would be most likely to reduce the technical difficulties in producing plastic from organic crops

A、a source of refining fossil fuels that significantly reduces their cost to plastic manufacturers
B、a way of maintaining grain yields while producing high quantities of plastic that do not interfere with the functioning of plant chloroplasts
C、a means of reducing the clean-up cost of environmental damage wrought byCO₂ and SO₂ emissions
D、a means of yielding greater efficiency from coal-based fuels used in the organic plastic-production process
E、the discovery of a renewable source of plant-sugar that would lessen reliance on fossil fuels in organic plastic-manufacture