Step 1: Understanding the Berne Convention.
The Berne Convention for the Protection of Literary and Artistic Works (1886) is the principal international agreement governing copyright. Step 2: Key provision.
It sets minimum standards for copyright protection and ensures that works originating in one member country are given the same protection in all other member countries. Step 3: Why others are wrong.
(a) Patents — covered under the Paris Convention, not Berne.
(b) Geographical indications — covered under TRIPS Agreement.
(c) Plant varieties — governed by UPOV Convention.
\[
\boxed{(d)}
\]