Statement I says domestic petrol and diesel prices have stayed flat, while Statement II says international crude prices have risen a lot. If Statement II were directly causing Statement I, domestic retail prices would normally be expected to rise too, following the global trend, but they haven't moved, which breaks that expected link.
This mismatch suggests the two observations come from separate, independent factors, government price-stabilisation policy on one side and global supply-demand dynamics on the other, rather than one directly causing the other.
So option 3, that both are independent causes, is correct.