The correct answer is c) Estuaries and lagoons.
Estuaries are partially enclosed coastal bodies of water where the tide meets the river. They are formed when a river meets the sea and the fresh water from the river mixes with the salt water from the sea. Lagoons are also partially enclosed coastal bodies of water, but they are formed when sandbars or barrier islands block off a bay or inlet from the open ocean.
Kerala’s coastal plain is characterized by estuaries and lagoons because it is located on the Arabian Sea. The Arabian Sea is a tropical sea, and the climate in Kerala is tropical as well. This means that the weather is hot and humid all year round, and there is a lot of rainfall. The rainfall causes the rivers in Kerala to flood, and the floodwaters flow into the Arabian Sea. When the floodwaters meet the salt water from the sea, they form estuaries. The estuaries are home to a variety of plants and animals, including fish, shrimp, crabs, and birds.
The other options are incorrect because they do not accurately describe the coastal plain of Kerala. Sandy beaches are not common in Kerala because the coastline is mostly rocky. Rocky cliffs are also common in Kerala, but they are not the most characteristic feature of the coastal plain. Dense mangrove forests are found in some parts of Kerala, but they are not as common as estuaries and lagoons.