Answer: when it envolves the world
Explanation: if it has anything to do with the world observations are better than experimenting and much safer.
This would be Newton's first law of motion as it is a factual statement based on observations.
I would have to say probably d.
Blood moves very slowly through capillaries. As the blood moves through a capillary, nutrients, oxygen, and food leave the blood and enter the body cells. ... Capillaries are exchange vessels. Gases (oxygen and carbon dioxide), nutrients, and wastes pass in both directions across capillary walls.
Pregnancy. This hormone is also produced by some cancerous tumors.