Manganese nodules are an example of: a. hydrogenous sediments. b. cosmogenous sediments. c. biogenous sediments. d. volcagenic sediments. e. terrigenous sediments.

Option A, hydrogenous sediments

Explanation:

Hydrogenous sediments are made up of minerals suspended in water that precipitates out in due course of time thereby forming minerals. These sediments are found in a very small amount and generally constitute 0.5 to 1 % of the total ocean sediments. While cosmogenous sediments are made up of space materials falling on earth, biogenous sediments are made up of living organism remains, lithogenous sediments are made up of land. All manganese, ferromanganese and phosphite nodules are hydrogenous

Hence, option A is correct