Answer:
D. Observational study
Step-by-step explanation:
We are given that Nico looked around the cafeteria during the lunch to see whether people purchased lunch or brought their own.
It is known that:
1. 'Survey' means to question a wide variety of population about their views on a particular issue.
2. 'Simulation' refers to act out a situation or process in order to find some conclusions.
3. 'Experiment' represent a scientific procedure undertaken in demonstrate a fact or test a hypothesis.
4. 'Observational study' is to study the samples without the variables being under the control of the observer.
