Food chain in which microorganisms breakdown the food formed by primary producers is

The correct option is C Detritus food chain
Detritus food chain is the type of food chain in which the dead organic matter called detritus are utilized to maximum level and there is minimum wastage of organic material. In this, the primary source of energy is dead organic matter, that is leaves, plant parts and dead animals. The primary consumers are called as detritivores. These include bacteria, fungi, protozoans. They are saprophytes. They break down the food formed by primary producers.

Thus, the correct answer is 'Detritus food chain.'