length of the diagonal : D. 12 cm
The space diagonal of a rectangular prism is derived using the following formula:
d = √(l² + w² + h²)
l = 6; w = 5; h = 9
d = √6² + 5² + 9²
d = √36 + 25 + 81
d = √142
d = 11.916 ⇒ 12 cm
slant height of the given pyramid :
l = slant height
h = height
a = base radius
l = √h² + a²
i'm assuming that the pyramid base is also the base radius
l = √8² + 12²
l = √64 + 144
l = √208
I = 14.42 ⇒ 14cm
in the event that the pyramid base is not the radius, then 12/2; 6cm
l = √8² + 6²
l = √64 + 36
l = √100
l = 10 cm