Which of the following statements is true?
a. nuclear fusion involves the splitting of a nucleus; nuclear fission involves combining two or more nuclei.
b. reactors for nuclear fusion are much more realistic than are reactors for nuclear fission.
c. nuclear fusion produces much more energy than nuclear fission.
d. nuclear fusion requires a enough fissionable material present to create and sustain a chain reaction

How does the digestive system interact with the circulatory system? a. messages sent as electrical impulses from the digestive system are transported throughout the body by the circulatory system. b. nutrients taken in and broken down by the digestive system are carried to various parts of the body by the circulatory system. c. nutrients and gases are absorbed by organs in the circulatory system. then, they are transported to all parts of the body by organs in the digestive system. d. oxygen and carbon dioxide are exchanged by organs in the digestive system, and the gases are carried to the rest of the body by the circulatory system.