Step 1: Understanding Section 27.
Section 27 of the Indian Contract Act declares agreements in restraint of trade as void, but trade combinations that aim to regulate trade (not restrict it) are exceptions.
Step 2: Evaluate options.
(a) Incorrect — there is an exemption for genuine trade regulation.
(b) Correct — exemption applies if the objective is regulation, not restriction.
(c) Misleading — Section 27 is the provision, but the reasoning is as in (b).
(d) Incorrect — correct reasoning exists.
\[
\boxed{(b)}
\]