I have a question from my real estate class. The present plumbing is copper. What type of plumbing should be used for repairs to prevent electrolysis?

Copper, CPVC or PEX are 3 options.

Your question has been aswered above.

FYI: In some municipalities they also allow PVC. Moreover, and technically speaking, you could use galvanized pipe with di-electric fitting installed at the point of connection with copper. Milo