Scientists from a state that has extensive agriculture want to sample the pollutants in areas with buffer strips and compare them to areas without buffer strips. Which sampling strategy would be most appropriate for the scientists to use when measuring pollutant levels in this scenario?

A.
1. Select locations every 100 kilometers along a single stream.
2. Record whether each location is near agricultural areas.
3. Record which agricultural areas have buffer zones.
4. Record which agricultural areas have no buffer zones.
5. Measure pollutants at each location.

B.
1. Identify all streams in the state.
2. Measure pollutants upstream of each agricultural area.
3. Measure pollutants downstream of each agricultural area.
4. Record data separately for the areas with buffer zones and those without.

C.
1. Select 10 streams with buffer zones.
2. Select one stream without a buffer zone.
3. Measure pollutants at the source of each stream.
4. Measure pollutants at the mouth of each stream.

D.
1. Select streams of similar sizes throughout the state.
2. Select 75 locations along the streams.
3. Include locations upstream and downstream of agricultural areas.
4. Include locations with and without buffer strips.
5. Measure pollutants at each location, recording the acreage of each agricultural area.