The answer to 2-7 would be -5, but 7-2 would be 5, depends how specific one is trying to be.
Hypotheses must be provable. If scientists cannot prove a "hypothesis" right or wrong, they need to change it to a legitimate hypothesis - something you can prove.
If it is proven wrong, they can change certain aspects of it to make a more specific experiment.
Answer:
Gas exchange between tissues and the blood is an essential function of the circulatory. The air contains oxygen that crosses the lung tissue, enters the bloodstream, and the alveoli are in direct contact with capillaries of the circulatory system. As water flows over the gills, oxygen is transferred to blood via the veins.
Explanation:
Greater then the water density, which has a density of 1 g/cm^3
A polar molecule has a positive and negative end because of electronegativity.