4 is what is knows as the factorial of 4.
4=4*3*2*1=24
Answer:
the correct answer is
D. 80 ft^3
vol. of pyramid = (l× w × h)/3
= (6×8×5)/3
= 80 ft^3
We will verify each options
option-A:

we can factor it



so, this is not irrational.........Answer
option-B:

Since, it can not be factored
so, this is irrational.........................Answer
option-C:

we can factor it



so, this is not irrational.........Answer
option-D:

we can factor it



so, this is not irrational.........Answer