The sea that is landlocked among the options provided is [D] Aral Sea. Situated between Kazakhstan and Uzbekistan, the Aral Sea was once one of the world’s largest lakes. However, due to extensive irrigation projects diverting its feeder rivers, the sea has become increasingly landlocked and has experienced significant shrinkage, leading to environmental and socio-economic challenges in the surrounding region. The Aral Sea’s diminishing size serves as a poignant example of the environmental consequences of human activity and underscores the importance of sustainable water management practices to preserve the integrity of ecosystems and safeguard natural resources.