A women with 47 chromosomes due to three copies of chromosome 21 is characterized by

The energy of second Bohr orbit of the hydrogen atom is $$-$$328 kJ mol^$$-$$1; hence the energy of fourth Bohr orbit would be

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species ?

The correct order in which the O $$-$$ O bond length increases in the following is