Answer:
A power plant using the lake water to cool the power plant
Step-by-step explanation:
i took the test and got it right 
Which of the following identifies the cause for thermal shock in a lake?
 A power plant using the lake water to cool the power plant
 Boaters frequenting the lake on weekends and spilling fuel into the lake
 Fishing tournaments that draw large crowds to the lake and leave trash behind
 People swimming in no swimming posted areas of the lake
Points earned on this question: 5