Which of the following is NOT a main category of commodities?

The category of commodities is generally divided into several main segments, which typically include metals, energy, and soft commodities. Metals include both base metals like copper and aluminum, as well as precious metals like gold and silver. Energy commodities encompass crude oil, natural gas, and coal. Soft commodities refer to agricultural products such as coffee, sugar, and cotton, which are grown rather than mined or extracted.

Plastic materials do not fit into the traditional classification of commodities. While plastics are used in numerous industrial and consumer applications, they are derived from petrochemicals and are not commonly traded on commodity exchanges in the same way that the main categories are. Therefore, identifying plastic materials as a non-main category of commodities is accurate.