民间审计是（）发展到一定阶段的必然产物，只要存在（），民间审计就有存在和发展的必要。
参考答案：商品经济；两权分离
白细胞分化抗原的生物学作用
John Preston was tired（）living in east London, in which he had moved after his wife's death.
A.to
B.of
C.at
D.for
