Passage VI
The concentration of dissolved oxygen (DO) in river water affects the fish in the river. Many freshwater fish species, including crappie, perch, and bass, require a minimum average DO concentration of 5 parts per million (ppm) to thrive. Other fish, such as carp and gar, can tolerate average DO concentrations as low as 3 ppm. Table 1 shows the DO concentration at saturation for water at various temperatures. Figures 1 and 2 show the measured changes in a river's water temperature and DO concentration, respectively, over a 24-hour period in midsummer. Table 2 shows how the DO concentration affects fish species in a river.
Table 1 and Figures 1 and 2 adapted from American ChemicalSociety, ChemCom: Chemistry in the Community, 2nd ed. ©1993 by American Chemical Society.
35. According to Figure 1.and Figure 2, what were the measured water temperature and DO concentration of the river water at 10 P.M.?
Your Answer is
Correct Answer is C
Explanation
Look at figure 1 first, at 10 PM, the river water temperature is 22°C;
Look at figure 2 again, at 10 PM, DO concentration is 9.2