f(x) . g(x) means that you have to multiply both functions.
This is how you do it:
[tex] \frac{4x^2 + 6}{2}. \frac{3}{2x^2+3} = \frac{2(2x^2+3).3}{2.(2x^2+3)}= 3[/tex]
Note that I have simplified the expressions that are common in the numerator and denominator.
Answer: option D. 3