The correct option is d.both a and b.
In fact, the strength of the electric field generated by a single-point charge is given by
[tex]E=k \frac{q}{r^2} [/tex]
where
k is the Coulomb's constant
q is the amount of charge that produces the field
r is the distance from the charge
We see from this formula that the strength of the electric field, E, depends only on the amount of charge that produces the field (q) and the distance from the charge (r), therefore options A and B are both correct.
