Mucus secreted by mucous membranes provides protection against infections by
A) forcing the pathogen to die in the struggle to free itself (like a fly strip).
B) trapping and removing pathogens.
C) phagocytosing pathogens by macrophages.
D) destroying pathogens by the complement system.
E) drowning the pathogen.
Ans: B) trapping and removing pathogens.
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Which public health measure(s) is/are MOST effective against pathogens transmitted through common vehicles?
A) water purification B) mosquito control C) food safety regulations D) water purification and food safety regulations
In the testing of water for coliforms, the presumptive test involves detection of
A. sheen production on a selective medium. B. a gram-negative nonspore-forming rod. C. gas production in a lactose broth medium. D. All of these choices are correct.
A single oak tree can support hundreds of beetles, caterpillars and other primary consumers. Such a phenomenon is an example of
A. a pyramid of biomass. B. excessive levels of primary production. C. an unusually diverse group of primary consumers. D. primary parasitism. E. an inverted pyramid of numbers.
Cells that produce antibodies and provide future immunity against similar pathogens are
A) mast cells. B) natural killer cells. C) T cells. D) dendritic cells. E) B cells.