Which of the following is NOT an example of a hazardous material?

Water is considered a non-hazardous material in most contexts because it is essential for life and generally safe to handle and use. While it's true that water can become hazardous in specific situations, such as flooding or having contaminants, in its pure form, it does not pose the same risks as the other materials listed. Chlorine and mercury are both toxic substances that can cause serious health problems if not handled correctly, and methane is a flammable gas that poses explosion risks. Thus, when identifying a material that is typically not classified as hazardous, water stands out as the clear choice.