Which of the following is not a natural cause of climatic change?
a. human activity
b. solar activity
c. earth's tilt
d. volcanic activity

the answer is option b.

explanation:

eutrophication happens when abundance supplements are available in oceanic biological systems, bringing about the expanded generation of vegetation and the resulting diminish in the oxygen levels of the water   eutrophication happens when there are abundance supplements in a waterway. this outcomes in plants having more sustenance and reproducing  more, here and there prompting more amphibian creature life also. eventually, this can decrease the oxygen level in the biological community.