The enzyme used to separate the double helix into 2 single strands is: helicase exonuclease ligase DNA polymerase

## Step 1<br />The question is asking for the name of the enzyme that is responsible for separating the double helix of DNA into two single strands. This process is known as unwinding the DNA.<br /><br />## Step 2<br />The enzyme that performs this function is called helicase. Helicase is a type of protein that is capable of breaking the hydrogen bonds that hold the two strands of DNA together.<br /><br />## Step 3<br />The other options provided, exonuclease, ligase, and DNA polymerase, are also enzymes that play roles in DNA replication. However, they do not perform the function of unwinding the DNA.<br /><br />## Step 4<br />Exonuclease is an enzyme that cleaves nucleotides one at a time from the end of a polynucleotide chain. This means it does not unwind the DNA.<br /><br />## Step 5<br />Ligase is an enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. This means it does not unwind the DNA.<br /><br />## Step 6<br />DNA polymerase is an enzyme that synthesizes long chains of DNA during replication. This means it does not unwind the DNA.