What is the correct meaning of pollution?

Correct answer: Introduction of harmful substances or energy into the environment

Pollution is the introduction of harmful substances or harmful forms of energy into the environment in amounts that can damage living systems or reduce environmental quality. Smoke, chemicals, sewage, plastic waste, and excessive noise are common examples. Thus, option C gives the correct meaning. Conserving natural resources, planting trees, and using water carefully are protective actions that can help prevent or reduce pollution; they are not pollution themselves. The key reasoning is to identify an unwanted contaminant or harmful energy entering air, water, or soil.