The main organ of the respiratory system is the lungs.
I think (C):600
Explained: other sources say there is about 650 but if you count the muscles within a complex muscle then about 840
By wearing a mask and social distancing
Answer:
The theory-data cycle
Explanation:
In the theory-data cycle, researchers or scientist want to collect new data to either test a theory, change the theory, or update an already existing theory. It is considered one of the most important science cycle. Franchesca in this case seeks to collect data to confirm an earlier research, and hence she does so to test the theory. Hence Franchesca used the process of theory-data cycle in conducting her study.