The activity that happens before the volcanic eruption is the expanding gases pushing magma through the pipe.
What do you mean by Volcanic eruption?
A volcanic eruption may be defined as an activity that is responsible for an opening in the earth's crust through which lava, volcanic ash, and gases exit.
Before the volcanic eruption, several gases create an extreme pressure that efficiently pushes the magma through the pipe which leads to the flow of lava onto the sides of the volcano.
Therefore, the correct option for this question is B.
To learn more about Volcanic eruptions, refer to the link:
https://brainly.com/question/17484682
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