To start the ejection process the oil feed to the centrifuge is first shut off and the oil remaining in the bowl removed by admitting （）.

A.faster than dead slow speed
B.slower than dead slow speed
C.with the output of MCR
D.at critical speeds

A.salinity
B.alkalinity
C.acid
D.sanitary

A.should be correctly carried out
B.should correctly be taken place
C.should carded with care
D.must to carry out with great care