Review the following list and select either an "h" if the item is a hazard, a "b" if it's a benefit, or "hb" if it can be both a hazard and a benefit. pyroclastic flows volcanic ash geothermal energy lahars lava flows volcanic materials (pumice, lava rock)

Pyroclastic flows, lava flows, and lahars are hazardous 
geothermal energy is beneficial
volcanic ash and volcanic materials can be both hazardous and beneficial

This questions somewhat depends on what the opinion who ever wrote the question so I don't know if all of what I said is correct according to your who wrote this but is what I believe is correct.  

I hope this helps.  Let me know if anything is unclear.