The correct answer is: b) Shallow sea.
The Palk Strait is a shallow sea that separates the Indian state of Tamil Nadu from the island nation of Sri Lanka. It is about 200 kilometers (120 mi) wide and has an average depth of only 10 meters (33 ft). The strait is a major shipping route and is also important for fishing and tourism.
A deep ocean trench is a long, narrow, steep-sided depression in the ocean floor. Trenches are formed when one tectonic plate is subducted under another. The deepest part of the ocean, the Mariana Trench, is located in the Pacific Ocean.
A volcanic crater is a bowl-shaped depression that forms when a volcano erupts. Craters can be very large, up to hundreds of kilometers in diameter. The largest crater on Earth is the Valles Marineris, which is located on Mars.
A river valley is a low-lying area of land that is formed by a river. River valleys are usually long and narrow, and they can be very fertile. The Nile River Valley is one of the most famous river valleys in the world.