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11. what are the two classes of pure substances?
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o a. solutions and mixtures
o b. liquids and gases
o c. elements and compounds
o d. atoms and molecules
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Consider the model of the oxygen cycle on earth. the majority of earth's oxygen reservoirs are found in the a) atmosphere. b) biosphere. c) hydrosphere. d) lithosphere.

Which type of respiration takes place when there is no oxygen present

Step 1 review the imaginary strand of dna below. note the complementary base pairs. a g c a a t c c g t c t t g g t c g t t a g g c a g a a c c step 2 to begin replicating this strand of dna, draw the two sides of the strand separating. step 3 now, draw the free-floating bases linking up with the separate sides. remember to follow the rules of complementary base pairing. step 4 draw the two resulting dna strands.