There are currently
22 active volcanoes in Luzon
428 in Visayas
and 20 in mindanao
Rainwater picks up carbon dioxide from the air and as it percolates through the soil, which turns into a weak acid. This slowly dissolves out the limestone along the joints, bedding planes and fractures, some of which become enlarged enough to form caves.
Answer:
I think it can be best described as sets