Lichens are a type of parasitic organism that often grow on rocks and trees in areas with dirty, polluted air. During a study of lichens and air quality in part of China, scientists measure the thickness of lichens and estimate how many rocks and trees are covered with lichens in one town. The scientists are following the scientific cycle of observing while using a systematic process, establishing facts, explaining facts, and then returning to the systematic process to collect more facts.

When scientists carefully measure the lichens and agree on their average thickness and how often they appear, which parts of the scientific cycle are the scientists using?

process and facts, because they are using a systematic method to measure and then record data
process and facts, because they are observing lichens and air quality and describing why they are related
explanation and process, because they are using a systematic method to measure and then record data
explanation and process, because they are observing lichens and air quality and describing why they are related