Answer
Option B is correct.
x² - 8x + 16 is the only perfect square trinomial among the options.
Step-by-step explanation
An expression that comes from the square of a binomial equation is a perfect square trinomial. For example, the result of the following will be a perfect square trinomial
(x + 1)²
(x - 4)² etc.
So, for this question, the option that can be expressed as a square will be the option that is a perfect square trinomial.
Option A
x² + 6x + 8
= x² + 4x + 2x + 8
= x (x + 4) + 2 (x + 4)
= (x + 2) (x + 4)
Not a perfect square trinomial
Option B
x² - 8x + 16
= x² - 4x - 4x + 16
= x (x - 4) - 4 (x - 4)
= (x - 4) (x - 4)
= (x - 4)²
This is a perfect square trinomial.
Option C
x² + 4x + 8
This cannot even be expressed in real number factorized form.
Option D
x² - 9
= (x + 3) (x - 3) (Difference of two squares)
Not a perfect square trinomial
Hope this Helps!!!