Fossils, or preserved parts of organisms from the distant past, have shown that species change over time. Radiometric dating can be used to determine the age of fossils by measuring the how much of the radioactive materials in each rock layer have broken down.
Answer:
A downhill
Explanation:
A runoff happens when water drags sediment from a rock over a sloping terrain. Thus, water drags the eroded fragments of a rock in favor of gravity, pushing these fragments downwards. This is very common in mountainous and steep regions, without vegetation cover, where erosion caused by runoff is very high.
It shows that a scientist can be creative because they used the fish's coughing technique to search for contaminated water.