The correct options are
A Floodplains
B Alluvial Fans
When a river floods, a lot of rich sediments and minerals get deposited in the surrounding areas forming flat areas of land. This makes the floodplains fertile and extremely suitable for agriculture. Alluvial fans are formed when rivers carry sediments down the hills and deposit them on gentler slopes in a triangular area. These alluvial deposits are fertile and suitable for agriculture.