Question

why does dna replicate?
to create a new copy to replace the damaged original
new cells will have a copy of the dna
to create a duplicate copy in case the original gets damaged

Explanation:

DNA replication is essential for cell division. When a cell divides, each new cell (daughter cell) needs a complete set of genetic information (DNA). So, DNA replicates so that new cells will have a copy of the DNA. The first option is incorrect because DNA replication is mainly for cell division - to provide DNA to new cells, not just to replace a damaged original (though DNA repair mechanisms exist separately). The third option is also incorrect as the primary purpose is not just having a duplicate in case of damage (again, repair mechanisms are more about fixing damage rather than replication being for that).

Answer:

New cells will have a copy of the DNA.