Three point charges $+q,-2q$ and $+q$ are placed at points $\left(x=0,y=a,z=0\right),\left(x=0,y=0,z=0\right)$ and $\left(x=a,y=0,z=0\right)$ respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are

$\sqrt{2}qa$ along the line joining points $\left(x=0,y=0,z=0\right)$ and $\left(x=a,y=a,z=0\right)$

$\sqrt{2}qa$ along $+y$ direction

$\sqrt{2}qa$ along $+x$ direction

$qa$ along the line joining points $\left(x=0,y=0,z=0\right)$ and $\left(x=a,y=a,z=0\right)$