I think it is B because it seems like the most valid choice.
Answer: Proximity to active volcanoes
Explanation:
When volcanoes erupt, they can generate tsunamis in the following ways:
-Parts of the volcano (some of them may be underwater) could collapse, generating a big displacement of water and resulting in a tsunami.
-The magma chamber could also collapse as it empties, also generating water displacement.
-If the volcanoes are near to the shore, debris resulting from the eruption could hit the water at fast speeds, producing big waves and eventually a tsunami.
In this case, the proximity of Palu city to active volcanoes, especially ones that are so close to the shore, increases the risk of a tsunami.
