Which of the following describes a positive feedback loop? When blood sugar concentration is too low, the endocrine system secretes hormones that increase blood sugar
concentration to a normal level.
When the body senses that the heart rate is very high, it secretes hormones that decrease the heart rate.
When blood sugar concentration is too high, the endocrine system secretes hormones that decrease blood sugar
concentration to a normal level.
O When someone is exercising intensely, the body secretes hormones that increase oxygen supply for cellular
respiration

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

•there must be variation for the particular trait within a population.

•the variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).

•individuals with one version of the trait must produce more offspring than those with a different version of the trait.good

explanation:

kelp are large brown algae that live in cool, relatively shallow waters close to the shore. they grow in dense groupings much like a forest on land. these underwater towers of kelp provide food and shelter for thousands of fish, invertebrates, and marine mammal species.

e) all of the above