Which one of the following is an example of a natural climate forcing?

Volcanic eruptions are a natural climate forcing, injecting ash and gases that shift the climate.

They occur without human action, unlike the other factors listed.

Greenhouse gases here act as a human-driven forcing from fossil fuel use.

Land-use change is a human-driven forcing from farming and deforestation.

Tropospheric aerosols largely come from human emissions and count as anthropogenic forcing.

Volcanic sulphate aerosols reflect sunlight and can cool the planet for a year or two.