The answer is the option "c"
The eruptions are caused by an accumulation of gases that press under a volcano.
The molten rock continues to generate upward pressure but can not advanced; this causes that its force increases with the passage of time, since it continues accumulating hot gases trying to come to the surface.
Finally, the surface yields and a volcanic eruption occurs.
Answer:
Oxygen (O2) concerntration
Temperature
pH
The data has to be verifiable by the scientific community.
