What is a positive feedback?

Which statement is true about the cell theory? a) it is well-supported by evidence. b) it is unchangeable and permanent.

What macromolecule is produced during translation? a. carbohydrate b. rna c. dna d. protein

In many humans, exposing the skin to sunlight over prolonged periods of time results in the production of more pigment by the skin cells (tanning). this change in skin color provides evidence that -