A town wants to detect a chemical spill that would pass down its river in about six hours. Its sensor records one water sample each year. What is the main flaw in this monitoring plan?

A county wants to track how much of a valley changed from farmland to houses between 2010 and 2025. Which monitoring method fits that goal best?

A wetland restored along a stream in 2018 traps sediment from a nearby farm field. Sediment carried by the stream measured 55 grams per 100 liters in 2019 and 22 grams per 100 liters in 2024. What does this five-year trend show?

Students test grass strips of four widths, 1 m, 2 m, 4 m and 8 m, along a field edge and measure the mass of soil washed past each strip. What is the independent variable?

A class studies whether a wetland lowers the nitrogen in runoff. They sample water at the same time of day, with the same bottle size, from the same stream, before and after the wetland. What is a controlled variable in this study?

A team monitoring pollution from a farm samples the stream both upstream and downstream of the fields. What does the upstream station add to the study?

A town needs a filter that removes at least 80 percent of a pollutant and costs no more than 50,000 dollars. Filter A removes 95 percent and costs 160,000 dollars. How should Filter A be judged?

A town needs a filter that removes at least 80% of a pollutant and costs at most $50,000. Filter B removes 84% for $45,000, Filter C removes 70% for $20,000, and Filter D removes 88% for $90,000. Which filter meets both needs?

A well is measured each year to see how far below the ground the water sits. Readings were 12 m in 2015, 18 m in 2020 and 24 m in 2025. What does this monitoring record show about the area's groundwater?

Measuring the same stretch of river every week for two years gives a trend, while measuring it once gives only a single snapshot.

A city records the amount of dust in its air. Which record counts as quantitative data?

Five water samples from one site read 6.9, 7.0, 7.1, 7.0 and 12.4. The team later found the fifth bottle had not been rinsed after holding a cleaning liquid. What best explains the odd reading?

A monitoring team collects five water samples at each site instead of one, then reports the mean. Why does the team work this way?

Over ten years a city planted many street trees, and its recorded dust levels fell. Traffic in the city also fell over those same years. What conclusion do these data support?

In a growing town, the share of ground covered by pavement rose from 20 percent to 55 percent, and the water running off streets during storms rose too. Which human impact do these paired records track?

Two identical sloping fields were watered the same way. The field with a cover crop lost 210 grams of soil into its sediment trap, and the bare field lost 880 grams. Which conclusion do these data support?

A farm wants to cut the water it uses on a crop while keeping the crop watered. Which method matches that goal best?

A study needs to know how many liters of water each house uses in a month. Which record gives that quantity?

A design team tests three roof gardens. Roof 1 holds the most rainwater but is heaviest. Roof 2 is lightest but holds little water. Roof 3 is light and holds a middle amount. What does the team gain by testing all three?

A company claims its new device removes pollution from a stream. Which evidence would best settle whether the claim holds?