Which procedure increases holding time when deicing|anti-icing a

Which procedure increases holding time when deicing|anti-icing an airplane using a two-step process?

A.Heated Type 1 fluid followed by cold Type 2 fluid.

B.Cold Type 2 fluid followed by hot Type 2 fluid.

C.Heated Type 1 or 2 fluid followed by cold Type 1 fluid.

正确答案是A