Answer:
B. documenting average rainfall of the area
Step-by-step explanation:
I believe this answer choice is correct because all the other choices are involved in predicting volcanic eruptions.
small earthquakes can indicate a shift in some tectonic plates, gasses being produced can indicate that a volcano may be "getting ready" to erupt, ad infrared imaging can detect heat which can show if a volcano has a tendency to erupt soon.
I am not 100% sure of this answer choice, but good luck!