How long before walking after an ankle sprain?

Which of the following is an example of a non-falsifiable hypothesis? a. there is a teacup orbiting the milky way galaxy. b. there is no life on mars. c. the human species started in africa. d. humans cannot live without the amino acid methionine

Epinephrine is a hormone released from the adrenal gland of the body, most often in a stressful situation. it is known as the "fight-or-flight" hormone. one way that it causes a response in the body is to activate receptors on muscle cells. where are these cellular receptors located? a. on the cell membrane b. in the nucleus c. on the cell wall d. around the mitochondria

What must be true for natural selection to heppen