A two dimensional flow has velocities in $x$ and $y$ directions given by $u = 2xyt$ and $v = -y^{2}t$, where $\text{t}$ denotes time. The equation for streamline passing through $x=1,\:y=1$ is

1. $x^{2}y=1$
2. $xy^{2}=1$
3. $x^{2}y^{2}=1$
4. $x/y^{2}=1$