“A centrifuge consists of an electric motor driving a vertical shaft on the top of which is mounted the bowl assembly”.According to this sentence, we can know that is mounted on the top of the vertical shaft（）

单项选择题The treatment of the fuel oils involves storage, heating, filtering and（）

A.centrifuging
B.pressurizing
C.atomization
D.igniting

单项选择题When anaerobic bacteria convert the sewage to an inert sludge,（）

A.no oxygen is needed
B.oxygen is necessary
C.oxygen is given off
D.no gas is produced

单项选择题Bacteria which live are said to be aerobic（）

A.in the presence of oxygen
B.without oxygen
C.in the presence of nutrition
D.without nutrition

单项选择题It is that reduce the BOD by converting the organic content of the sewage to a chemically and organically inert sludge（）

A.the bacteria
B.oxygen
C.oxidizing function
D.agitation function

单项选择题The basic process of biological sewage treatment consists of the liquor either by bubbling air through it or by agitating the surface（）

A.oxygenating
B.oxidizing
C.deoxygenating
D.proportioning