Final answer:
Morsetown Creek is the creek that is the source of 30-50% of pollutants in Greenwood Lake.
Step-by-step explanation:
The source of 30-50% of the pollutants in Greenwood Lake is Morsetown Creek. The information provided in the question does not mention the other creeks, so we cannot determine the percentage of pollutants coming from other sources. However, Morsetown Creek plays a significant role in the pollution of Greenwood Lake.