Which one of the following hydrolyses internal phosphodiester bonds in a polynucleotide chain?

The enzyme that hydrolyses internal phosphodiester bonds in a polynucleotide chain is an endonuclease. Endonucleases are a type of enzyme that cleave the phosphodiester bonds within a nucleotide chain, resulting in the formation of two smaller nucleotide chains. So, the correct answer is option C. Notice that the other options are not correct. Lipase is an enzyme that hydrolyses lipids, exonuclease is an enzyme that hydrolyses nucleotides from the ends of a nucleotide chain, and protease is an enzyme that hydrolyses proteins.