Which of the following is not true concerning the impact of volcanoes? a. acid rain can result from volcanic eruptions. b. tephra are a combination of water and rubble. c. damage can continue for years after the initial eruption. d. the volcanic explosion is the pyroclastic flow.

I would say that b and d are not true as tephra is just the pyroclastic fragments that are ejected from the explosive type of volcano and are not usually thought of as mixed with water and also an explosive volcano does not normally have flows but it has hot fragments ejected as chunks that are airborne unlike a say Hawaiian shield volcano made of basalt that flows with lava. Occaisonally there can be flows from an explosive volcano if the ash is mixed with water making a lahar, but this is relatively rare. The explosive type is usually a type of acidic volcano unlike basalt which is basic. Actually in b it is true because while tephra can be just the pyroclastic material like ash and bombs, it can also be mixed with water from the water vapour from the eruption.

B.a pop up at ion changes in response to a change in the environment.

Answer the collision of tectonic plates;