the first thing I would do would be to factor 6 out of 6x^2+30x+36. You should get
x^2 + 5x + 6.
Factoring this result is straightforward, since we see immediately that 2 and 3 are factors of 6, and that 2+3 = 5 (coeff. of the middle term).
A. x+2
B.x-6
C.x-2
D. x+6
From the above discussion, I see immediately that x-2 is a factor of the given trinomial. x-2 corresponds to the root 2, whereas x+2 corresponds to the root -2 (which does not belong here).