How do scientists forecast space weather why?

Well that's a not easy task. The specialized forecasters analyze near-real-time ground- and space-based observations to assess the current state of the solar  environment which includes the areas from the Sun to the Earth and points in between. Space weather forecasters also analyze the pattern of solar activity. 

That result from subduction of oceanic plates beneath lighter continental plates. most of the earth's volcanoes are located around the pacific ring of fire because that the location of most of the earth's subduction zones.

The answer is b on plato.