Please helpp I have no clue

Volcanic irruption is most likely to be violent when a) volcanoes near to the sea b) the neck of the volcano is sealed by a plug c) the lava is viscous d) the lava reaches the surface through a fissure e) the volcano is on the ocean floor

Me answer as many as you can what percentage more of water is used to provide us with electricity versus for irrigation? do we use more freshwater in our homes or to provide us with electricity?

Given: circle a externally tangent to circle b. how many possible common tangents to circles a and b can exist? 2 3 4