The "lub" heart sound represents ____
a. a heart murmur
b. closure of the atrioventricular valves
c. closure of the semilunar valves
d. hypertension
e. movement of actual heart muscle
ANSWER: b
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Tetrazolium chloride is used by the seed industry to indicate
(a) if a seed is undergoing photosynthesis. (b) if seeds are undergoing aerobic respiration. (c) if seeds are alive. (d) both b and c.
Based on the graph in Figure 45-1, which of the following statements is true?
a. The primary response to the initial injection subsided after seven weeks.
b. The primary response to the initial injection peaked at 102 antibody units.
c. The primary response to the initial injection was faster, but not as intense as the secondary
response.
d. The secondary response to the initial antigen was both faster and more intense than the
primary response.
e. The primary and secondary responses to the initial antigen were about equal.
The decrease of carbon-12 in a fossil indicates the age of that fossil
__________________ Indicate whether the statement is true or false.
What is the significance of having specialized epithelium and smooth muscle in the urinary bladder?
a. It helps reabsorb water. b. It helps reabsorb salts. c. It permits the diffusion of gases. d. It is capable of shrinkage and stretching. e. It protects the bladder from nitrogenous wastes.