Answer is Gasoline.
Explanation: For determining which substance will float, it can be determined with the values of density.
Density of Milk =
![1.026gm/cm^3](https://img.qammunity.org/2019/formulas/chemistry/high-school/kvsjaxqu5hoi8doejnmq2a0clowadxkuc8.png)
Density of Gasoline =
![0.702gm/cm^3](https://img.qammunity.org/2019/formulas/chemistry/high-school/vcgj33f3ur3cs0r2urp32hlr5jw08uthi1.png)
The one with lower density will float and the one with more will sink.
So here, we can see that the density of gasoline is less therefore, this will float.