Question

The triangular collection of sediments at the mouth of a river forms

a, delta
b, beach
c, arches
d, glaciers​

Answer 1

Answer:

When large amounts of alluvium are deposited at the mouth of a river, a delta is formed. The river slows down at the mouth, so it doesn't have the energy to carry all the silt, sand, and clay anymore. These sediments form the flat, usually triangle-shaped land of a delta.

Answer 2

Answer:

Glaciers

Explanation:

Glaciers is the triangular collections of sediments at the mouth of a river forums.