Use the vocabulary words from "Read It" to complete the following sentences.
Geologists use two main ways to find the age of rocks. When they
want an age in actual years, they find the (4)
This involves
looking at the radioactive decay of specific isotopes.

Ascientist wants to know how individual lions within a pride interact with each other in their own environment. to do this, the scientist sedates and tags all of the lions within a pride. then, he places several remotely-controlled video cameras near the lions' den and performs an observational field study. he collects continuous video footage over the span of one year, analyzes the video, and then forms conclusions based on his observations.