A square of side L meters lies in the x-y plane in a region, where the magnetic field is given by 
Tesla, where B0 is constant. The magnitude of flux passing through the square is
As we know that area vector is perpendicular to the plane of any polygon. So here square is in x-y plane then its area vector in z direction i.e. 
Also we know, magnetic flux is the dot product of magnetic field vector and area vector 
Given that 
putting the value of B and A in above equation i.e.
As we know that same unit vector is 1 and rest of all are zero because î,ĵ, k are all perpendicular to each other i.e. 
So option c is matching with our solution rest are not.
Therefore, (c) is the correct answer.
1