Which of the following environmental hazards is due primarily to human activities?

The environmental hazard that is due primarily to human activities is ozone depletion.

The ozone layer is a protective shield in the Earth's stratosphere that absorbs most of the Sun's harmful ultraviolet radiation. The thinning of the ozone layer is mainly caused by the release of man-made chemicals. The most significant contributors to this environmental hazard are chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS) which have been used in refrigeration, air conditioning, foam production, and aerosol propellants. When these chemicals reach the stratosphere, they break down ozone molecules, leading to what is known as the "ozone hole."

In contrast, the other environmental hazards listed—hurricanes, earthquakes, and volcanic eruptions—are natural phenomena. While human activities can influence the severity or impact of these events, such as through climate change exacerbating the intensity of hurricanes or human settlement in earthquake-prone areas, they are not primarily caused by human actions.