The main hazard from a quiet volcanic eruption is? ?

There are actually three primary hazards which involve lava, gases, and pressure.
A quiet volcanic eruption can release poisonous gases (such as sulfur compounds) which can poison the air or water supplies. Also, lava flows can create dangerous wildfires, and destabilize slopes leading to landslides. Additionally, they can add stress to underground rock formations and potentially trigger earthquakes.

True statement gravity force is more on bigger mass, less on smaller mass.all mass fall on planet with same acceleration and speeds

This is the most closely resembles the model.