Where does the sedimentary rock chalk form? from the precipitation of minerals in shallow marine environments by the lithification of glacial deposits by the compaction of wind-blown sand in eolian environments by the accumulation of microorganisms in deep marine environments

The correct answer is an accumulation of microorganisms in deep marine environments.

Chalk rock refers to a pure form of limestone produced in tropical and warm seas about 100 million years ago in the Cretaceous period. The microscopic marine algae known as coccoliths thrived in the ancient seas. Their shells were comprised of calcite. With the death of the algae, their bodies sunk to the floor of the sea and sediment of chalk got deposited.

Over many years layers of chalk sediment got deposited and resulted in compaction of loose sediment into solid chalk rock.