Explanation:

- To find the longest ladder that can fit inside the room, consider the room's diagonal.

- The formula for the diagonal of a cuboid is given by \(\sqrt{l^2 + b^2 + h^2}\), where \(l\), \(b\), and \(h\) are the room's length, breadth, and height, respectively.

- For this room, the diagonal calculates as \(\sqrt{56^2 + 34^2 + 8^2}\).

- Calculate each step:

- \(56^2 = 3136\)

- \(34^2 = 1156\)

- \(8^2 = 64\)

- Sum these squares = \(3136 + 1156 + 64 = 4356\).

- Find the square root: \(\sqrt{4356} = 66\).

- The longest ladder possible is 66 meters.

Therefore, Option:4 - 66 m is correct.