Right option is (b) Microbial dealkylation
The explanation: Microbial dealkylation, also known as Microbial demethylations helps to metabolize cresols to methyl catechols without loss of any substituent of alkyl group. Chemical precipitation is used to remove heavy metals by use of chemicals which ultimately leads to precipitation of the heavy metals but it doesn’t filter out. Activated Alumina and Reverse osmosis is used to filter out heavy metals.