What word best describes the beating of the heart and the circulation of blood?
- voluntary
- intermittent
- involuntary
- infrequent

Which sentence best expresses the differing opinions of these two book reviews?

Aperson with age is more likely to catch diseases that healthy people usually don’t catch. what are these infections called?

Photosynthesis uses co2 and cellular respiration produces co2. we call the point when the two processes are in balance--when there is no net production of co2--the compensation point. how might you limit one of the processes in order to achieve a compensation point?