The method of preparing compost with the help of earthworms is called
Option (b) is the correct answer.
The process of converting organic materials including plants and animal waste into manure is called composting. The method of preparing compost with the help of redworms is called vermicomposting. The material that results from the process is called vermicompost. Vermicompost contains a large amount of worm castings which are rich in organic nutrients required for plant growth.