The correct answer is - It is a geyser that formed due to water heated by magma erupting at Earth's surface.
Old Faithful is the best known of the geysers in Yellowstone National Park. It is a very big geyser that shoots the boiling hot water relatively high.
The formation of Old Faithful is due to the geological activity in the region. There's lot of volcanic activity in this area, so there's also lot of magma in the area. Because there are lot of cracks in the crust, as well as the magma being very close to the surface, the water is heated deep into the ground. The high pressure contributes to the hot water to be shoot out around 32 meters into the air.
Old Faithful is one of the biggest tourist attractions in Yellowstone National Park, and it is also the first geysers in this area that got its own name back in 1870.