Here's a problem to solve: An experiment is being conducted to determine the air quality inside a building. In order to come to a conclusion, scientists must gather data. Which of the following would be an excellent source of data from which to draw a conclusion?

Among the 4 following options, which is the correct answer?

- A: naked-eye viewing
 
- B: calculations of air mass
 
- C: demonstrations of air pressure
 
- D: measurement of airborne particulates
 