参考答案：B

解析：

译文：国家信托是一个（ ）。 通过关键词The National Trust(专有机构名称，没有替换形式，可在原文中直接找到) The National Trust in Britain plays an increasingly important part in the preservation for public enjoyment of the best that is left unspoiled of the British countryside. Although the Trust has received practical and moral support from the Government, it is not a rich government department. It is a voluntary association of people who care for the unspoiled countryside and historic buildings of Britain.从原文中可知，该机构不是财力雄厚的政府部门，而是民间的志愿者组织。因此B选项Non-profit organization depending on voluntary services.依靠志愿者服务的非营利性组织。最为符合原文的意思。（第一自然段符合行文顺序，原文表达的意思的重组(restatement),并且本质意思（essential meaning）相同）