Not A. or B. because product means mutiplying.
Not C. because 6*2 does not equal to 8.
Answer : D.
Explanation :
(3x+6)(4x+2)
(3x)(4x)= 12x^2
(3x)(2)=6x
(6)(4x)= 24x
(6)(2)= 12
12x^2+6x+24x+12
12x^2+30x+12