The best answer is B - the fish die.
Acid rain flows through soils. If the soil part of a watershed, aluminum is released from the soil and into the streams and lakes located in that watershed.
This lowers the pH in the lake from between 6 and 8 (which is the normal pH in lakes and streams) to less than 5.
Both increase of aluminum and lower pH are directly toxic to fish and they kill off fish populations
