Two masses \(m\) and \(\frac{m}{2}\) are connected at the two ends of a massless rigid rod of length \(l\). The rod is suspended by a thin wire of torsional constant \(k\) at the centre of mass of the rodmass system (see figure). Because of torsional constant \(k\), the restoring torque is \(\tau  = k\,\theta \) for angular displacement \(\theta \). If the rod is rotated by \(\theta _0\) and released, the tension in it when it passes through its mean position will be

1. A \(\frac{{3k\,\theta _0^2}}{l}\)
2. B \(\frac{{2k\,\theta _0^2}}{l}\)
3. C \(\frac{{k\,\theta _0^2}}{l}\)
4. D \(\frac{{k\,\theta _0^2}}{2l}\)