The table below shows the salmon population, in thousands of pounds, in columbia river, from 1870 to 1950. year salmon population (in thousands of pounds) 1870 10,200 1890 20,000 1915 20,500 1931 30,000 1950 10,000 based on the table, which of these is most likely the period during which a series of large hydropower units were built on the columbia river? a. between 1870 and 1890 b. between 1890 and 1915 c. between 1915 and 1931 d. between 1931 and 1950

Option D, between 1931 and 1950

Explanation:

The hydraulic structure of dam has some sub structures which interferes with the natural navigation of the fishes within any water body.  

Due to such interference the fishes get diverted to a different path of flow and hence are not accountable.  This causes reduction in the number of fish counts.

The higher the construction of dams, the higher will be the effect of it on the fish navigation which will ultimately lead to reduction in fish count.  

Hence, option D is correct.

format change of dna.  

thinking it would be physical characteristics