Correct choice is (c) Microfiltration
Explanation: Microfiltration is a membrane filtration process which removes contaminants from a fluid by microporous membrane. The membrane pore size ranges from 0.1 to 10 micrometers. Microfiltration is different from reverse osmosis and nanofiltration because it does not require pressure and does not remove dissolved contaminants. However, centrifugation is often effective when the particles are very small and difficult to filter.