D
Below is a question with multiple-choice answers. Choose the correct option based on your reasoning.

### Question:
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?

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

### Answer:
