Rate me 1 - 10
lol I lied and said that a picture of me was my friend but this is me lol

How about an okay 7? Maybe an 8 or 9. But also now that this is a school website and you could always be exposing yourself to pedos.

The answer; They used a stable isotope and tracked it with a Becquerel counter

An example of stable  isotopes is 14-C and 2-H. These types of isotopes have an atomic decay that leaves less radioactive material behind, hence safe for laboratory use and used without harming the normal processes of life being investigated. Bq is the unit preferred for this type of radioactivity.