Explanation: Hints: অনুভূমিক পাল্লা, \( R = \frac{v_0^2 \sin 2\alpha_0}{g} \) উচ্চতা, \( H = \frac{v_0^2 \sin^2 \alpha_0}{2g} \) \([g = 9.8 \, \text{ms}^{-1} = 980 \, \text{cms}^{-1}]\) Solve: মোট অনুভূমিক দূরত্ব, \( R = 10 \, \text{cm} + 10 \, \text{cm} = 20 \, \text{cm}, \alpha_0 = 45^\circ \) \( R = \frac{v_0^2 \sin 2\alpha_0}{g} \implies v_0 = \sqrt{\frac{Rg}{\sin 2\alpha_0}} = \sqrt{\frac{20 \times 980}{\sin (2 \times 45^\circ)}} = 140 \, \text{cm} \) \( H = \frac{140^2 \times \sin^2 45^\circ}{2 \times 980} = 5 \, \text{cm} \) Ans. (A)