Correct option is A
The correct answer is: (a), A-III, B-IV, C-II, D-I

A floodplain is a plain formed by the deposition of sediments carried by a river during flooding. These sediments, primarily alluvium, are deposited over time, resulting in a flat, fertile plain suitable for agriculture.
An abyssal plain is a large, flat, and relatively featureless area of the deep ocean floor. These plains are located at depths of 3,000 to 6,000 meters below sea level and are primarily composed of fine-grained sediments deposited over millions of years.
A loess plain is formed by the accumulation of wind-blown sediments known as loess. These plains are characterized by fertile soils derived from the fine-grained, wind-deposited sediments, which are often found in regions with strong prevailing winds.
An outwash plain is formed by the deposition of sediments carried by meltwater streams flowing away from a glacier. These plains are characterized by a mixture of sands, gravels, and other glacial debris deposited by the flowing water.