The function of the "ciliary escalator" is to
A) propel inhaled dust and microorganisms toward the mouth, away from the lower respiratory tract.
B) remove microorganisms from the gastrointestinal tract.
C) remove microorganisms from the lower respiratory tract.
D) trap microorganisms in mucus in the upper respiratory tract.
E) trap inhaled dust and microorganisms in mucus and propel it away from the lower respiratory tract.
E
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HIV is classified as a retrovirus because
A) it infects only cells with a CD4 receptor. B) it makes a DNA copy of its RNA once inside the host cell. C) this virus is composed of two cells surrounded by a lipoprotein coat. D) it reverts to an inactive form when it infects B lymphocytes. E) it causes the production of HIV antibodies.
Mass extinctions
A. may have been due to changing environments caused by continental drift. B. may have been due to climatic changes after meteorite collisions. C. have occurred at least 5 times in the Earth's history. D. All of the choices are correct.
Which group is most distantly related to green algae?
A. Ciliates B. Dinoflagellates C. Diplomonads D. Apicomplexans E. Diatoms
In cohesion-tension theory, what molecular interactions allow water molecules to maintain a continuous fluid column as water is pulled from roots to leaves?
A. Ionic bonds B. Covalent bonds C. Hydrogen bonds D. Polar bonds E. Nonpolar bonds