Explanation: \(\text{Hints: } T = 2\pi\sqrt{\frac{L}{g}}\) \(\text{Solve: } T = 2\pi\sqrt{\frac{L}{g}} \implies T^2 = 4\pi^2 \times \frac{L}{g} \, [L = \text{দৈর্ঘ্য প্রসারণ}]\) \(\implies L = \frac{T^2g}{4\pi^2} = \frac{(1)^2 \times 10}{4 \times (\pi)^2} = 0.25\, \text{m}\) \(\text{মোট দৈর্ঘ্য } = 1 + 0.25 = 1.25\) \(\text{Ans. (C)}\)