Which of the following fire extinguishing agents are currently restricted by the government?

Halon is recognized as an effective fire suppression agent, particularly in areas where sensitive equipment is involved, such as in computer rooms or on aircraft. However, it is currently restricted by government regulations due to its harmful effects on the ozone layer. The use of Halon has been banned in many situations under the Montreal Protocol, a global agreement aimed at protecting the ozone layer by phasing out the production and consumption of ozone-depleting substances.

In contrast, other agents such as carbon dioxide, water, and dry chemical extinguishers remain widely accepted and are not subject to the same restrictions. Carbon dioxide is effective for certain classes of fires, water is a common extinguishing agent for many combustible materials, and dry chemical extinguishers are versatile and suitable for a range of fire types. Therefore, Halon's restriction is specifically due to environmental concerns, making it the correct answer in this context.