3 : 4

3 : 5

4 : 5

16 : 15

D. 16 : 15

For an income of Re. 1 in 9% stock at 96, investment = $Rs.\left(\frac{96}{9}\right)=Rs.\frac{32}{3}$

For an income Re. 1 in 12% stock at 120, investment = Rs. $\frac{120}{12}$ = Rs. 10.

Ratio of investments = $\frac{32}{3}$ : 10 = 32 : 30 = 16 : 15.