Lagoon is a shallow stretch of water partially or completely separated from the sea.
E.g: Chilka lake in Odisha, Pulicat lake in Tamil Nadu and Andhra Pradesh and Vembanad lake in Kerala are the famous lagoons in India

Cirque, Aretes, U' Shaped Valley

Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loop comes closer and closer. In due course of time the meander loop cuts off from the river and forms a cutoff lake, also called an Ox-bow lake.

Erosion is the wearing away of the landscape by different agents like water, wind, ice and sea waves.

As the cavities of sea caves become bigger, only the roof of the caves remain to form sea Arches. When erosion further breaks the roof, only walls are left, thus forming stacks.

Due to continuous erosion and deposition of rivers along the sides of the meander, the ends of the meander loop comes closer and closer

(i) Winds erode the lower section of the rock more than the upper part.
(ii) An isolated residual hill, standing like a pillar with rounded tops are called Inselbergs. E.g. Inselberg in the Kalahari Desert of South Africa.
(iii) When the wind blows, it lifts and transports sand from one place to another. When it stops blowing the sand falls and gets deposited in low hill - like structures. These are called sand dunes. The crescent shaped sand dunes are called Barchans
(iv) When the grains of sand are very fine and light, the wind can carry it over very long distances. When such sand is deposited in large areas, it is called Loess. Large deposits of loess are found in China.

(c) 1, 2 and 3

1 and 3