Which of the following is the MOST COMMON cause of membranous conjunctivitis?

Organism most commonly causing membranous conjunctivitis is Corynebacterium diphtheriae and Streptococcus pyogenes. Membranes formed by bacteria can be true membrane or pseudo membranes. The true membrane is formed after more severe inflammation and the exudate has a high fiber content and coagulation occurs in the epithelium so that on being stripped the epithelium remain attached to the membrane leaving a raw bleeding surface. In case of pseudomembranes, there is coagulation of exudate on the surface of epithelium and on being stripped there are no underlying bleeding points. Ref: Textbook of Ophthalmology edited by Sunita Agarwal page 885.