Given data
*The given height is h = 3.1 m
*The value of the acceleration due to gravity is g = 9.8 m/s^2
The formula for the impact velocity is given by using the conservation of energy as
![\begin{gathered} (1)/(2)mv^2=mgh \\ v=\sqrt[]{2gh} \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/mhlqbk1nuapt7xtxi1on51km3ow0dwephw.png)
Substitute the known values in the above expression as
![\begin{gathered} v=\sqrt[]{2*9.8*3.1} \\ =7.79\text{ m} \\ \approx7.8\text{ m} \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/rbep3bffbu7x9h5nxw9s8v38gflmypmsr9.png)
Hence, the impact velocity is v = 7.8 m/s and the correct option is (D)