The correct answer is option 4 - flood basalt eruption. The Deccan Traps is a large volcanic province located in western India. It is composed of layers of flood basalts, which are formed by extensive volcanic eruptions of basaltic lava flows.

Option 1 - Shield eruption: Shield volcanoes are typically formed by relatively quiet eruptions of basaltic lava that spreads out in thin layers. While shield eruptions can form large volcanoes, they do not typically result in the formation of extensive layers of basaltic lava flows like the Deccan Traps.

Option 2 - Composite eruption: Composite volcanoes, also known as stratovolcanoes, are formed by explosive eruptions that produce thick layers of both lava and pyroclastic materials. Composite eruptions are characterized by a mix of volcanic ash, rocks, and lava. The Deccan Traps, however, are primarily composed of basaltic lava flows, which is not characteristic of composite eruptions.

Option 3 - Caldera eruption: Caldera eruptions occur when a volcano collapses into an empty magma chamber after a large eruption. The collapse leads to the formation of a large depression or caldera. While calderas can result in the release of