Which of the following is an example of an offshore reference cell?

Zinc is correctly identified as an offshore reference cell primarily due to its electrochemical properties and suitability for cathodic protection systems in marine environments. Offshore structures, such as pipelines and platforms, often utilize zinc reference electrodes because they provide stable measurements in seawater, which is crucial for monitoring the cathodic protection levels of submerged structures.

Zinc electrodes are favorable because they have a well-defined and predictable potential when exposed to seawater conditions. This makes them reliable for determining the effectiveness of the cathodic protection systems used to prevent corrosion of metal structures in the harsh marine environment.

In contrast, while stainless steel, copper, and iron have their uses in various applications, they do not serve as effective reference cells in offshore environments due to issues like less stable potentials, susceptibility to corrosion, or lack of compatibility with seawater conditions. This further reinforces zinc's role as a preferred choice for offshore applications.