After seeing a serger demonstration at a local home show, dressmaker Carla knows it would be beneficial. She decides to look up Sergers on ISEW.com, an open forum where multiple unpaid contributors expound on a multitude of topics. Carla is using what type of source for her information search?

a$.$ Nonmarketing$-$controlled information source

b$.$ Consumer$-$to$-$consumer reviews

c$.$ Internal information

d$.$ Marketing$-$controlled information source