Answer:
a. preventing the cross-linkage of NAM subunits
Step-by-step explanation:
The bacterial cell wall is made of peptidoglycan which is a polymer of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) residues. The NAM residues are crosslinked to impart additional strength to the cell wall.
Most of the antibiotics that target the cell wall synthesis in bacteria inhibit the enzyme of transpeptidation which in turn cross-links the NAM residues of the polysaccharide chains of the bacterial cell wall. Examples of these antibiotics include penicillins and cephalosporins.