Which one of the following discoveries involving dna happened first? a) avery discovered that dna was responsible for storing and passing information through generations. b) sequencing an entire human genome was completed. c) griffith learned that a chemical changed harmless cells into harmful cells. d)hershey and chase used bacteriophages to confirm that dna was the genetic material in genes

From the given options, the following sidovery involving DNA happened first: C) Griffith learned that a chemical changed harmless cells into harmful cells. 
The British medical officer named Frederick Griffith discovered DNA in 1928 while conducting experiments using Streptococcus pneumoniae bacteria and mice. 
He concluded that the living R bacteria had been transformed into pathogenic S bacteria by an unknown, heritable substance from the dead S cells that allowed the R cells to make capsules.

It is either a or b not sure but i think its mostly a

They both determine the exact age of rocks.