Which of the following explains why most elements in the periodic table have a decimal number for their atomic mass?
a. most elements have different isotopes.
b. most elements have different number of electrons.
c. most elements have different numbers of protons in the nucleus.
d. most elements are not found in nature.

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."