Answer:
1. A fossil that is widespread geographically but only occurs in one layer or a small number of layers of rock
2. Sediment deposited into water will spread in a horizontal and continuous sheet
3. Any undisturbed sequence of layered rocks has the oldest rock on the bottom and newest rock on the top
4. Study of fossils
5. Study of rock layers and the process that form them
Sorry if any of these are wrong