What does NARC stand for?

Any material such as straw, sawdust, leaves, plastic films, & loose soil that is spread upon the surface of the soil to protect the soil & plant roots from the effects of raindrops, soil crusting, freezing or evaporation:

Organic evolution through large discontinuous variations was propound by________?

The aggregation of individual particles is called________?

Reciprocal recurrent selection is effective with________?

Inorganic constituents vary in size from fine clay particles ________ mm to large ________ mm gravel and rock: