Planets in our solar system do not revolve around the sun in perfect circles. their orbits are more like ovals that scientists describe as which of the following?
a. revolutionary
b. rotational
c. periodical
d. elliptical

Daughter element the new element produced along with a decay particle in a nuclear transmutation 2. half-life the substance that decays in a nuclear transmutation 3. parent element the change of one chemical element into another by nuclear decay or radioactive bombardment 4. transmutation the time required for the decay of one-half of the atoms in a sample of radioactive material