The heart, liver, and stomach are each examples of
a. a tissue.
b. an organ system.
c. a nerve.
d. an organ.

The correct answer is D. an organ

This is NOT an example of an organ system, as a system implies that they work together for a common goal; your heart has nothing to do with your digestive system.

I got a 100% on my test, so I know this is correct.

stratosphere: as the altitude increases, the air temperature increases. the stratosphere has a layer of ozone, called the ozone layer. this layer absorbs most of the ultraviolet radiation from sunlight. this results in the stratosphere being warmer.

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.