Answer:
Option c
Step-by-step explanation:
The study is an observational study. An observational study is made when the researchers collect data based on what they see, hear or observe without any form of manipulation or treatment plan from the researchers. Thus, in this case, the study is an observational study because the study examines individuals in a sample, but does not try to influence the response variable/influence their responses.
Answer:
and 
Step-by-step explanation:
Given

per section

Required
Model the scenario
The model of this scenario is:

This gives:
<em />
<em> -- This represents the multiplication model</em>
Divide both sides by 18



Reorder
<em />
<em> -- This represents the division model</em>
18cm (A). Remember to get the radius when you have the circumference is to ALWAYS divide it by 2. 36/2 = 18
Recall that the derivative of a constant is 0.