Where are most or the Earth's active volcanoes concentrated at present?

Answer: Option C

In Pacific Ocean, the Earth's active volcanoes concentrated at present. Volcanic eruptions occur only in certain places and do not occur randomly. This is because the Earth's crust is broken into a series of slabs known as tectonic plates. Most volcanoes are found along a belt, called the "Ring of Fire" that encircles the Pacific Ocean.