Indicate which numbered feature (1 to 5) in the schematic drawing below of the DNA double helix corresponds to each of the following. Your answer would be a five-digit number composed of digits 1 to 5 only, e.g. 52431.

( ) Hydrogen-bonding
( ) Covalent linkage
( ) Phosphate group
( ) Nitrogen-containing base
( ) Deoxyribose sugar