Fossils tell us about the long history of life on the earth and so far, our fossil record probably represents of all species that have ever lived.

C.about 10% i think

Magma is outside the volcano  and lava is inside the volcano. 

Answersource rock;

Explosive eruptions are the most hazardous, involving large volumes of tephra and gases emitted from the volcano. lahars, pyroclastic flows, ashfall, and many other volcanic hazards are commonly associated with explosive eruptions. explosive eruptions are very dangerous. basically, any form of hazard can occur.