Answer:
(3h+y)*(3h-y)
Explanation:
We are given the following expression:

We want to find the LCD for:
9h²-y² and 3h + y.
3h+y is already in it's most simplified way.
9h²-y² , according to the notable product of (a²-b²) = (a-b)*(a+b), can be factored as:
(3h-y)*(3h+y).
The factors of each polynomial is:
3h + y and (3h-y)*(3h+y)
The LCD uses all unique factors(If a factor is present in more than one polynomial, it only appears once).
So the LCD is:
(3h+y)*(3h-y)
Which is option B.