Textile Mills Often Release Dye Color and Toxic By-Products into Rivers

Textile mills often release dye color and toxic by-products into rivers and streams, which may then taint groundwater. Fungi associated with mangrove trees have been shown to reduce both colors and toxicity in tainted groundwater.
-Suppose that fungal treatment was added to stream water contaminated from a textile mill. The toxins in the water tend to lower pH levels, and scientists wanted to study how adding the fungal treatment affected stream pH levels. pH levels were recorded every year for five years. Results indicated that the acidity of the stream water decreased from pH 2.5 in the first year to pH 5.9 by the fifth year. Scientists concluded that

A) the fungal treatment had little to no effect on detoxifying the stream water.
B) the fungal treatment had a positive effect on detoxifying the stream water.
C) the fungal treatment had completely detoxified the stream water.
D) there was not enough evidence to determine the effects of the fungal treatment on the toxic stream water.