Answer:
An increase in the algae in the neighborhood lake could be related to Sarah's farm as a result of the use of fertilizer.
Step-by-step explanation:
Fertilizers can be used washed into the lake during the rain downpour. When such happens, the fertilizer provides food for the algae already in the lake which can lead to a dramatic increase in the population of the algae.
Take samples from the neighborhood lake reveal that there are high levels of phosphorus and nitrogen which are the key compositions of most fertilizers.
Therefore, it is likely that the lake contains some of the fertilizer that where washed from Sarah's farm.