Which factor affects the same percentage of a population regardless of the population’s density?

Flood

The factor which affects the same percentage of a population is Flood

A flood is an overflow of water on land which is usually dry. Sometimes a water resource such as river, lake or pond gets flushed with too much water and sometimes heavy rains cause floods and devastate the population. The same percentage of a population regardless of the population's density is affected by the flood no matter what is the density of the population.

i have to report this, it doesn't relate to biology

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given bodies of water

pacific / arctic / indian / southern

[ a ] the caribbean sea

[ b ] the northern ocean

[ c ] the atlantic ocean

[ d ] the barents sea

with this being the given answers