Final answer:
In the presence of Mg2+ only, the transcription factors that are normally bound to the Psf promoter are MetA, MetB, and MetC.
Step-by-step explanation:
In the presence of Mg2+ only, the transcription factors that are normally bound to the Psf promoter are MetA, MetB, and MetC. This is because MetA binds to the A site, MetB binds to the B site, and MetC binds to the C site in the promoter region. These binding sites are important for regulating the transcription of the Psf gene. Therefore, the answer is (d) MetA, MetB, and MetC.