Answer: B

Reasoning: Microwave polymerization heats the acrylic uniformly, so residual monomer does not vaporize and form voids; studies of denture-base PMMA cured in a microwave show very low or clinically insignificant internal porosity compared with conventional water-bath curing, while other properties (shrinkage, color, surface gloss) are not markedly improved [Yannikakis, 2002, 12131882; Shlosberg, 1991, 2640122].