I would have to say (D.) if it's been 150 years.
Answer:
The circulatory system circulates the blood to the whole body.
The respiratory system brings oxygen to the blood, and the circulatory system circulates the oxygenated blood to the cells.
Explanation:
Observation is a factual statement that cannot be changed or replaced.
Explanation)
Hypothesis is a tentative statement that can be tested.
Scientific law and theory are considered a fact but can be disproven if new evidence emerges.