推断判断题。由题干定位至第四段。由首句Humans have been growing food crops for 10,000 years可知，A中more than与原文不符，故排除；由but the effort to produce fuel down on the farm is in its fancy可见B错；由段中 We’re at such a basic stage，可知，从作物提取燃料还处于初级阶段，C正确；由本段倒数第二句可知cell walls是由four hemicelluloses, along with cellulose and lignin构成，并且由a cell wall engineered to include more hemicellulose可知一个细胞壁不仅仅只有four hemicellulose(半纤维素), 排除D。