JoAnn has a cold. She is coughing up mucus (a respiratory secretion) from her lungs. JoAnn is the a. portal of exit b. reservoir c. portal of entry in the chain of transmission. The mucus from her cough is the a. reservoir b. portal of exit c. portal of entry in the chain of transmission.
The answer is B, because the mucus is coming OUTSIDE her body. Hope that helps.