What is the most common threat to the human body from an invading virus?
a. viral fluids will be produced in the bloodstream.
b. acids will ferment in the digestive system.
c. viral reproduction will destroy once healthy cells.
d. muscle tone in the heart will be stimulated.

c. viral reproduction will destroy once healthy cells.

exposure to hazardous carcinogens and toxic substances can cause breathing problems, such as copd and various types of cancer. it also increases the risk of heart attacks and strokes and has serious (but no less unattractive) side effects, such as aging, yellow teeth, a terrible smell and damage to the vocal cords.