Form the greatest and smallest numbers using the digits $5,2,9,7$ (each digit is used only once). What is the difference between the two numbers formed?

The correct option is B

$7173$

Find the greatest and smallest and their differences:

The given digits are $5,2,9,7$.

A condition is given that each digit can be used only once while forming numbers.

So, the greatest number $=9752$

And, the smallest number $=2579$

Now, the difference between the greatest and the smallest number formed using the digits using $5,2,9,7$ can be calculated as,

The required difference $=$ greatest number $-$ smallest number

$\Rightarrow$the required difference $=9752-2579$

$\Rightarrow$the required difference $=7173$

Hence, option B is the correct option.