The correct option is A 3(x−2)
6(x2−4)=2× 3× (x−2)× (x+2).
15(x+2)(x+7)=3× 5× (x+2)× (x+7).
Hence, the common irreducible factors between 6(x2−4) and 15(x+2)(x+7) are 3 and (x-2).
The least exponents of these factors are respectively 1 and 1.
Hence, the HCF = 31× (x−2)1=3(x−2).