Which of the following toxins acts by inhibiting protein synthesis -: (A) Cholera toxin, (B) Shiga toxin, (C) Pertussis toxin, (D) LT of enterotoxigenic E.coli
Answer is B. Toxin which acts by inhibiting protein synthesis:

Diphtheria toxin and Pseudomonas Exotoxin A: Inhibiting elongation factor 2
Shiga toxin and Verotoxin (Shiga like toxin) of EHEC: Inhibiting 60s ribosome