When one neuron communicates with another a <em>synapse</em> passes the <em>signals</em> betwen them.
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The answer to your question is A
A volcanic eruption produces lava, ash and gases. ... Volcanoes cause limited erosion directly; the underside of a new lava flow scours topsoil or loosely consolidated sediments. Volcanic eruptions are the indirect causes of substantial erosion through the action of volcanic debris on the atmosphere, land and water.
