The correct option is C +1
Formal charge on any atom is calculated as:
Formal charge (FC) = V − L − B2
Where,
V = Total number of valence electrons in the atom.
L = Total number of non bonding(lone pair) electrons in the atom.
B = Total number of bonding (shared) electrons in that particular atom.
For the given structure, we have V = 5 ; L = 0 ; B = 8
∴ Formal charge on the nitrogen atom in NH+4(ammonium) ion is:
FC=5−0−12×(8)∴FC=1
The formal charge on nitrogen in case of NH+4(ammonium) ion is +1.