Three of the pairs below name a sudden natural disaster and the material that comes rushing down or across in it. Choose the pair that does not fit that classification.

In a tsunami sea water sweeps across the coast, in an avalanche snow slides down a mountainside, and in a landslide rock and soil break away and fall. The monsoon is a wind that brings rain over a whole season; a season is a stretch of time and not a material, and the monsoon is an expected yearly visitor rather than a sudden disaster, so this pair fails the rule twice over.