What is Aphthous stomatitis?

Which of the following is a major cause of injury

Mucous membranes.. a. cover or line external surface of body. b. line internal body surfaces that are in contact with the environment. c. produce antibodies to combat infection. d. secrete sweat, which has antibacterial enzymes.

Which of these are fast-acting compounds that attack ocygen-dependent tissues known to be particularly sensitive to these compounds? a.nerveb.vesicantsc.cyanide compoundsd.pulmonary