Answer:
I am confused on what this is supposed to be, but if you are talking about chemicals, then your answer is sulfur.
Hoped this is what you're looking for. Sorry if it isn't. I would love to help, but it needs to be more specific.
Answer would be B. Earthquakes happen most of the time when a volcano is about to erupt.
Answer:
C: larger river systems
D:fewer geographic barriers
Explanation: I just did it