In What Ways Are Radioactive Isotopes Potentially Harmful

In what ways are radioactive isotopes potentially harmful?

A) Unmonitored release into the environment can make changes in a cell's DNA.
B) They are used to trace molecular changes.
C) They are used to destroy abnormal cells.
D) They are used to determine the age of biological specimens.
E) They are used to trace the path of materials throughout the body.