In the constant pressure filtration, the filter cake is incompressible and the medium resistance can be ignored. If the operating pressure difference increases by 1 times, the filtration rate increased to______. 恒压过滤时， 如滤饼不可压缩，介质阻力可忽略，当操作压差增加1倍，则过滤速率为原来的_______。（ ） A. 1 B. 2 C. 20.5 D. 1/2