What percentage of the world's photosynthetic activity is accomplished by phytoplankton in the euphotic zone?

A. 70
B. 60
C. 50
D. 40
E. 30


Answer: D

Environmental & Atmospheric Sciences

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Which of the following is true of a 100-year flood?

A) A 100-year flood occurs every 100 years on a given stream. B) The probability of a 100-year flood occurring on any given year is 1:100. C) A 100-year flood cannot occur twice within 10 years. D) The probability of a 100-year flood is related to how recently the last 100-year flood occurred.

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The third-most abundant gas in Earth's atmosphere (not including water vapor) is

A) oxygen. B) argon. C) nitrogen. D) carbon dioxide. E) helium.

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A ________ is a one-sided fold connecting horizontal or gently inclined strata.

A) syncline B) overthrust C) symmetrical fold D) anticline E) monocline.

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Coral bleaching occurs when

a. corals reproduce. b. fish move into coral reefs. c. zooxanthellae (algae) leave the coral. d. coral reefs expand their range.

Environmental & Atmospheric Sciences