Step 1: Recall the IS 456:2000 provision for longitudinal reinforcement.
As per IS 456:2000, the spacing of longitudinal bars measured along the periphery of a column shall not exceed
\[
300\,\mathrm{mm}.
\]
Step 2: Identify the correct option.
Hence,
\[
\boxed{300\,\mathrm{mm}}
\]
is the correct answer.
Therefore,
\[
\boxed{(A)}
\]
is the correct answer.