Which of the following is a chemical change?
a. silver tarnishing as the silver metal reacts with sulfur
b. soil drying as water evaporates
c. a solution of salt water being diluted as water is added to it
d. a rock eroding as the wind removed particles from it

Silver tarnishing as the silver metal reacts with sulfur

Explanation:

It is a chemical reaction because the metal is changing its chemical composition due to the sulfur

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."