The correct option is (b) Rennet
For explanation: Rennet hydrolyzes the peptide linkage between phenylalanine and methionine residues in the casein protein present in the milk. This results in the release of a hydrophilic oligopeptide and the hydrophobic para-k-casein which removes the protective effect and allows coagulation of the milk to form curds, which are then compressed and turned into cheese.