Based on the compounds of group 15 elements, the correct statement(s) is (are)

Basic character of oxide decreases as we move down the group. Bi2O5 is more basic than N2O5- Covalent nature depends on the electronegativity difference between bonded atoms. NF3 is more covalent than BiF3 - Boiling point of NH3 is more (due to H-bonding) than PH3 - P–P  single bond is stronger than N–N single bond (as in N, due to smaller size of atoms lone pairlone pair repulsion will be more)