The nucleus of some isotopes, such as radium-226 shown above, will spontaneously undergo nuclear decay. These isotopes are said to be radioactive.

What causes the nucleus of an isotope to be radioactive?
A. an unstable ratio of protons and neutrons
B. the attraction of protons to electrons
C. exposure to toxic chemicals
D. too many electrons in its orbitals

In the nineteenth century, gregor mendel first determined some basic rules of genetics that have been observed throughout all types of life. no observations have disproved these basic rules of genetics. charles darwin developed the idea of biological evolution around the same time, but he was unaware of mendel’s discoveries in genetics. over a century later, darwin’s idea of evolution was modified in order to incorporate mendel’s rules of genetics along with the other evidence that darwin had used. what is most likely the relationship between mendel’s rules of genetics and darwin’s idea of biological evolution? a.)mendel’s genetics states laws that are now part of the theory of biological evolution.b.)biological evolution states laws that are part of mendel’s theory of genetics.c.)mendel’s genetics replaced darwin’s entire concept of biological evolution.d.)biological evolution is a law that explains why all genetics exist.