How does the number of electric field lines passing through a unit area depend on the distance from a point charge?

Two charges $+4e$ and $+e$ are at a distance $x$ apart. At what distance must a charge $q$ be placed from charge $+e$ so that it is in equilibrium?

$A$ deuteron and an $\alpha$-particle are placed $1\,\mathring{A}$ apart in air. The magnitude of the intensity of the electric field due to the deuteron at the position of the $\alpha$-particle is:

Two non-conducting spheres of radii $R_1$ and $R_2$ and carrying uniform volume charge densities $+\rho$ and $-\rho$,respectively,are placed such that they partially overlap,as shown in the figure. At all points in the overlapping region:
$(A)$ the electrostatic field is zero
$(B)$ the electrostatic potential is constant
$(C)$ the electrostatic field is constant in magnitude
$(D)$ the electrostatic field has same direction

Which of the following is not a unit of electric field?

$A$ semi-infinite non-conducting rod lies along the $+x$-axis with its left end at the origin. The rod has a uniform linear charge density $\lambda$. The magnitude of the electric field $|\vec{E}|$ at a point on the $y$-axis at a distance $L$ from the origin will be: