单选题
For seven days after the mud-slide, they had only grass and tree leaves to {{U}}subsist upon{{/U}}.
【正确答案】
C
【答案解析】[分析]习语辨析
subsist upon表：维持生活，生存；A．made food out of用……制造食物；B．substitute for beds用……来代替床；C．live upon by eating靠吃……生活；D．insist on keeping to themselves坚持保守秘密；因此C为答案。