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
\((a-b)(a+b) = a^2-b^2\)
In the first option, we have
\((5x+3)(5x-3)\)
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 .
