When centrifuging heavy fuel oil, an important factor to consider is the _____（1) flow rat

When centrifuging heavy fuel oil, an important factor to consider is the _____(1) flow rate; (2) viscosity of the fuel oil.

A.(1) only is correct

B.(2) only is correct

C.both (1) and (2) are correct

D.neither (1) or (2) are correct

请帮忙给出正确答案和分析，谢谢！