The fovea centralis has the highest concentration of
A. rhodopsin.
B. cones.
C. night vision receptors.
D. rods.
B. cones.
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Which of the following tissue types is characterized by having cells suspended within an extracellular matrix consisting of a mixture of fibrous proteins and carbohydrates?
A. nervous B. muscular C. epithelial D. connective E. digestive
Which of the following statements about leptin and obesity is correct?
a. Obese people tend to have unusually low levels of leptin. b. As a result of low levels of leptin in obese people, food cravings are not regulated adequately. c. Obese people often develop resistance to leptin and thus appetite is not suppressed. d. A diet high in saturated fats tends to block leptin production and thus stimulates appetite
Which type of plants are best adapted to hot, dry conditions?
a. C3 b. C4 c. CAM d. C3 and CAM e. C4 and CAM
Viral infections are difficult to treat because
a. there are no drugs to treat virus infections. b. medicines can’t reach viruses inside cells. c. vaccines are ineffective against viruses. d. we do not yet understand how viruses work. e. all of these are true.