Cathodic protection of a metal pipe against corrosion usually entails .
Options:
A. attaching an active metal to make the pipe the anode in an electrochemical cell.
B. coating the pipe with another metal whose standard reduction potential is less negative than that of the pipe.
C. attaching an active metal to make the pipe the cathode in an electrochemical cell.
D. attaching a dry cell to reduce any metal ions which might be formed.
E. coating the pipe with a fluoropolymer to act as a source of fluoride ion (since the latter is so hard to oxidize).

C. attaching an active metal to make the pipe the cathode in an electrochemical cell.

Explanation:

Cathodic protection is a technique which helps in controlling the increased rate of corrosion of a metal surface by making it the cathode of an electrochemical cell. It connects the metal to be protected to a more easily corroded which is usually referred to as the sacrificial metal to act as the anode.

This technique preserves the metal by providing a highly active metal that can act as an anode and provide free electrons. By introducing these free electrons, the active metal sacrifices its ions and keeps the less active steel from corroding.