The first step of the trichrome permanent stain (70% alcohol plus iodine step)...

(a) Is necessary with all specimens preserved in mercuric chloride-based PVA fixative
(b) Is necessary for specimens preserved in copper-based and zinc-based PVA fixative
(c) Is necessary for all specimens no matter what preservative is used
(d) May be eliminated if using the low viscosity mercuric chloride-based PVA fixative