The protection provided by the mucous membrane against pathogenic invasion is not enough. The mere ingestion of tubercle bacilli or picornaviruses in sufficient numbers will lead to penetration of GIT mucosa. A similar penetration of respiratory tract by___ can occur following a heavy exposure to these pathogens :

Options

A. Pneumococci
B. Rhinoviruses
C. Salmonella
D. Both 1 and 2

Answer

D