Final answer:
The phosphodiester bond is the type of bond that connects neighboring subunits in a DNA strand, forming the sugar-phosphate backbone.
Step-by-step explanation:
The type of bond that holds together neighboring subunits in a single strand of DNA is the phosphodiester bond. These bonds form the sugar-phosphate backbone of the DNA strand. Specifically, phosphodiester bonds are covalent bonds that connect the 3' carbon of one sugar molecule to the 5' carbon of another sugar molecule in the nucleic acid structure. This is distinct from the hydrogen bonds that connect two complementary strands of DNA to create the double-helix structure. Hydrogen bonds, while critical for the overall structure of DNA, are weaker than the covalent bonds and allow DNA strands to 'unzip' for replication. The correct answer to the question is C: phosphodiester bond.