Which can have the most impact on an ecosystem?

unnatural occurrences
natural occurrences
abundant resources
volcanic eruptions

The correct answer is unnatural occurrences.

Explanation:

The unnatural occurrences refer to the catastrophic incidents created due to human activities that can impart deleterious effects on the ecosystem. These activities exhibit the most impact on a specific ecosystem. This may comprise forest fire, deforestation, road building, mining explosions, and others.  

These activities are considered harmful as it may lead to the destruction of various species because of the damage resulting to the non-living physical environment.  

option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.