The answer would be D. Because the iron fillings are attracted to the magnet underneath the glass.
Answer:
a. ρ
b. 
Explanation:
a. To find the density of magnetic field given use the gauss law and the equation:
,
,
Ω,
,
, 
ρ
ρ
ρ
ρ
b. The electric field can be find using the equation:




It is because the potential energy is similar to MgH.
When it comes to MgH, it means mass, gravity and height respectively.
By using the value of acceleration, seema will find the potential energy of a ball.