Final answer:
The yeast two-hybrid system's primary purpose is to detect protein-protein interactions by visual means, using the interaction of a split transcription factor to activate a reporter gene.
Step-by-step explanation:
The purpose of the yeast two-hybrid system is best described by option (b), which states that it provides visual detection of protein-protein interactions. This biological technique utilizes a split transcription factor composed of a DNA-binding domain (BD) and an activator domain (AD). The BD is fused to the 'bait' protein, and the AD is fused to the 'prey' protein. When these proteins interact, they bring together the BD and AD, restoring the function of the transcription factor and initiating transcription of a reporter gene. Consequently, the activation of the reporter gene indicates the interaction between the bait and prey proteins.
The advantage of yeast cells over bacterial cells to express human proteins, like the one mentioned in the question, lies in that yeast cells are eukaryotic. Yeast cells can modify proteins in a manner that's more similar to human cells. This similarity extends to essential cellular processes, including the utilization of G-protein coupled receptors for signaling, which are evolutionarily conserved across yeast and human cells.