d
Dipole moment is the product of magnitude of charge and seperation between charges.

i.e., \(P=q \times d\)

here compound is \(HCl\),you know as well, \(HCl\) is ionic compound in which one electron transfers from hydrogen to chlorine.

so, magnitude of charge on dipole, \(q =1.6 \times 10^{-19} \,C\)

and seperation between charges \(=\) bond length \(=1.26 A ^{\circ}=1.26 \times 10^{-10} \,m\)

so, dipole moment, \(P =1.6 \times 10^{-19} \times 1.26 \times 10^{-10}\, Cm\) \(=2.016 \times 10^{-29}\, Cm\)

we know, \(1 D =3.335 \times 10^{-30}\, Cm\) [ Debay, \(D\) is the unit of dipole moment ] \(=2.016 \times 10^{-29} /\left(3.335 \times 10^{-30}\right)\)

\(=20.16 / 3.335\)

\(=6.0449\, D\)

now, percentage ionic character \(=\) experimental value/ theoretical value \(\times 100\) \(=1.03 \,D / 6.0449 \,D \times 100\)

\(=0.170 \times 100\)

\(=17.00\, \%\)