Ans. is 'd' i.e., Inhibition of protein synthesisToxinsMechanism of actionBotulinum toxinActs on the peripheral nervous system (i.e. neuromuscular junctions) by inhibiting myoneural junction acetylcholine release and cause flaccid paralysis (many strains of Clostridium botulinum synthesized C2 toxin, that ADP- ribosylates actin, thereby inhibiting its polymerization, affecting the shape of target cells, and resulting in enterotoxin activity in vivo).Diphtheria toxinInhibits protein synthesis in target cells by catalyzing the ADP ribosylationof a novel amino acid (diphthamide) on elongation factor 2, a host protein required for translocation of ribosomal messenger RNA.Pertussis toxinActs by ADP ribosylation of several members of the family of guanine nucleotide-binding (G) proteins involved in signal transduction, inhibiting their function and affecting a variety of effector systems, such as adenylate cyclase, phospholipases, and several types of ion channels.ST of E. coliActivates guanylyl cyclase to increase cGMP.V cholerae toxin LT of E. coliActivates adenylate cyclase of the intestinal epithelial cell by ADP ribosylation of the stimulatory G protein, Gs - | cAMP.Shiga toxinInhibits protein synthesis by enzymatic inactivation of the 28S RNA within the 60S ribosomal subunit.Verocytotoxin of E. coliInhibit protein synthesis by inhibiting ribosomal function (same as shiga toxin)