单选题 Knowledge is a comfortable and necessary retreat and ______ for us in an advanced age; and if we do not plant it while young, it will give us no shade when we grow old.
【正确答案】 C
【答案解析】ingredient“原料，要素”；reliance“信赖，信心”；shelter“庇护，避难所，遮 盖物”；inclination“倾向，爱好”。根据句意和各个选项的意思可知，正确答案是c。