Step 1: Relativism spectrum.
- Universalism: HR valid everywhere (option b).
- Strong cultural relativism: culture is the principal source of moral validity, though a few universal minima may exist.
- Radical/absolute relativism: culture the sole source (option a — too extreme).
Step 2: Evaluate options.
(a) Overstates to “sole”; captures radical relativism.
(c) Ties HR to municipal law positivism, not cultural relativism per se.
Hence (d) best represents strong cultural relativism.
\[
\boxed{(d)}
\]