Explanation

(d)
$aG + bH \rightarrow Products$
Suppose order of reaction =n
When concentration of both G and H doubled then rate increases by eight times.
$rate = k(reactants)^{n}$
$(8) = k(2)^{n}$
$(2)^{3} = k(2)^{n}$
n=3
When concentration of G is doubled keeping the concentration of H fixed, the rate is doubled.
$Rate = \lbrack G\rbrack^{1}$
then,
$Rate = \lbrack G\rbrack^{1}\lbrack H\rbrack^{2}$