Colds cannot be treated with antibiotics because
A) it is not known what causes colds.
B) antibiotics do not kill viruses.
C) the bacteria that cause colds are resistant to antibiotics.
D) antibiotics only work before symptoms appear.
The success of vaccines relies on which type of immune cell?
A) macrophage
B) natural killer cell
C) neutrophils
D) memory cells
Allergies are due to
A) decreased natural killer cell numbers.
B) exposure to certain microbes.
C) the release of histamine by mast cells.
D) the production of antibodies by macrophages.
The incidence of allergies has increased in recent years due to all of the following EXCEPT
A) increased exposure to microbes.
B) smaller family size.
C) less exposure to animals.
D) use of antibiotics and vaccines to prevent diseases.
All of the following are correct about vaccines EXCEPT
A) they can be prepared from weakened pathogens.
B) they can cause autism.
C) they allow the body to develop immunity to a pathogen without being ill.
D) they induce active immunity.