单选题 The only solution to rubbish problem for a nation which now spends more on wrapping food than it pays farmers to produce it, is recovering ______ the packaging materials for commercial as well as for conservation reasons.
A. on sale B. on the spot
C. on a large scale D. on all sides

【正确答案】 C

【答案解析】[解析] on a large scale“大规模地”；on sale“出售”；on the spot“当场；在现场”，用在句中语义不明确；on all sides“四面八方”，也不合适。