Sediment smaller than 0.0625 mm in diameter cannot be seen unaided and is called . Sediment between 0.0625 and 2 mm in diameter generally is known as , and grains larger than 2 mm are called .

Silt, Sand and Gravel

Explanation:

When rock wears out due to process of weathering, it breaks down into pieces or sediments  that ranges from microscopic  grains to very large grains. Now,

Sediment smaller than 0.0625 mm in diameter cannot be seen unaided and is called Silt

Sediment between 0.0625 and 2 mm in diameter generally is known as Sand which  refers to collection of  fine, medium, and coarse sand.

Grains larger than 2 mm are called Gravel and range from 2 mm up to 64 mm.

c, this answer is productivity.