The graphing is shown below
Answer:
Observational Study
Step-by-step explanation:
Because she stands by the front door and records each student
After 2.0 years, the 4.0 mg sample decays to 2.0 mg.
After another 2.0 years (total 4.0 years), the 2.0 mg sample decays to 1.0 mg.
And after another 2.0 years (total 6.0 years), the 1.0 mg sample decays to 0.50 mg.
So it takes 6.0 years for 4.0 mg to decay to 0.50 mg.
