The correct option is D 15 : 32
If two simple ratios are expressed like a single ratio as the ratio of product of antecedents to product of consequents, then it is called as compound ratio of the given two simple ratios.
Thus, the compound ratio of 5 : 8 and 3 : 4 is (5 × 3) : (8 × 4) = 15 : 32.