What is most likely true of a person who has this heart rhythm?
the person is taking drugs to prevent blood clots.
the person has had a heart transplant.
the person is having a heart attack.
the person has hypertension.

The organelle pictured is found in cells of and is theorized to have once been an independent organism.

What percentage of light hits earth's surface directly?

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis