Which of the following is a harmful effect of oil spills? (a)migration of large schools of fish (b)changes in sea level (c)plant photosynthesis decreases (d)increased ocean ph

C) Plant photosynthesis decreases

Explanation: An oil spill may impact on various ways, it can be harmful to plants and animals, change the ph of the water (which also affects the wildlife in the water), dangerous emissions, and one thing you need t to have in mind is that these effects may last from 2 to 5 or more years.

Then the two options that made sense are options C and D.

The change in the Ph made by the oil spills is the opposite of the showed in option D, the Ph decreases, which made the water more acidic, so we can discard the option D.

And we end up with option C, plant photosynthesis decrease, this is because the thicker oil blocks the sunlight to the plants underwater, and then there is less sunlight received by them, which affects their photosynthesis.