In this question, we have to find all the products which result in a difference of perfect squares .
The formula of the difference between squares is

In the first option, we have

Which is of the form of difference of two squares. And similarly , the last option is also in the form of difference of two squares .
And for perfect squares, we have same factor twice in b and e, so for that b and e are the correct options .
So out of the given options, correct options are a,b,e and f .