Ehrlich phenomenon seen in:

Ans. is 'c' i.e., Corynebacterium(It is due to presence in toxin preparation of varying amounts of toxoid and antitoxin to combine in varying proportions and is called Ehrlich phenomenon).Ehrlich defined the minimum lethal dose (MLD) of the diphtheria toxin as the least amount of toxin required to kill a guinea pig weighing 250g within 96 hours after subcutaneous inoculation.