The figure shows the electric field lines around three point charges $A, B$,and $C$.
$(a)$ Which charges are positive?
$(b)$ Which charge has the largest magnitude? Why?
$(c)$ In which region or regions of the picture could the electric field be zero? Justify your answer.
$(i)$ Near $A$ $(ii)$ Near $B$ $(iii)$ Near $C$ $(iv)$ Nowhere

(A) The electric field lines for charges $A$ and $C$ are directed outwards,which indicates that $A$ and $C$ are positive charges.
$(b)$ The magnitude of a charge is proportional to the number of electric field lines originating from or terminating at it. By counting the lines,we observe that charge $C$ has the largest number of field lines associated with it. Therefore,charge $C$ has the largest magnitude.
$(c)$ The electric field can be zero only at a point where the electric fields due to individual charges are equal in magnitude and opposite in direction. This can occur between two like charges. Since $A$ and $C$ are both positive,the electric field can be zero in the region between $A$ and $C$. Because the magnitude of charge $C$ is greater than that of charge $A$,the neutral point (where the field is zero) will be closer to the charge with the smaller magnitude,which is charge $A$. Thus,the electric field could be zero in the region near $A$.