Oxygen was necessary in the atmosphere before
A. photosynthesis could occur.
B. life could begin.
C. metabolism could occur.
D. aerobic respiration could occur.
D. aerobic respiration could occur.
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The antiviral drugs currently approved for use in HIV disease include
A. protease inhibitors. B. nucleoside reverse transcriptase inhibitors. C. fusion inhibitors. D. nonnucleoside reverse transcriptase inhibitors. E. All of the choices are correct.
A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds. The F1 plants have yellow seeds. What is the expected phenotypic ratio of seed color of the offspring of an F1 × F1 cross?
A) 1:2:1 B) 2:1 C) 3:1 D) 9:3:3:1
Which structures make up the innermost whorl of a flower?
a. the receptacles b. the carpels c. the sepals d. the stamens
Scientists assign each kind of organism a universally accepted name in the system known as
a. traditional classification b. the three domains c. binomial nomenclature d. cladistics