The substance which has definite composition with definite physical and chemical properties is said to be pure substance. These substances are not separated by the different physical techniques such as filtration, distillation, evaporation etc.
The clear water pumped from a deep aquifer is a pure substance because water is a pure compound which consist of constant single type of atoms or group of atoms and water has specific value of boiling and melting point. Water is also not separated into units or constituents by physical technique.
Hence, clear water pumped from a deep aquifer is a pure substance.
Evaporation of the solution
Fossil C is the youngest. Layers further down were placed earlier than others. Because C is on the top layer, it must be the youngest (unless a disaster mixed up all the layers!).
Answer: A index fossil is any animal or plant preserved in the rock record of the earth that is characteristic of a particular span of geologic time or environment. A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time.
Explanation:
