The graph below shows the salmon population, in thousands of pounds, in the columbia river, from 1866 to 1983.

based on the graph, which of these conclusions is most likely correct?

select one:
a. the salmon did not breed between 1866 and 1879.
b. the hydropower units on the river were deactivated after 1970.
c. a series of large hydropower units were built on the river after 1931.
d. a large amount of contaminants were present in the river between 1910 and 1912.

d. A large amount of contaminants were present in the river between 1910 and 1912.

Explanation:

If you observe the graph and the options you can see that the salmons definetely breed between 1866 and 1879 since the population in pound of salmons increased to almost its historical maximum, and the other options are the activation of the hydropower units, and since both options, 1931 and 1970 after the given events in one it decreased the population and in the other it increased, so they cancel eachother, so the only option that matches the graph would be that a larg amount of contaminants were present in the river between 1910 and 1912, since the population decresead largely.