Answer:
C. E/2, F.
Step-by-step explanation:
Suppose two particles as A and B which are separated by a distance of r.
And the charge on the particle A is +2q and the charge on the particle B is +q.
According to the question, the electric field at a distance of r on the charge +2q is E.
.
And the force on the +q charge at a distance of r is F.
.
Now, the electric field can be calculated at +q charge on the same distance will be,

Now substitute E/2 for
in the above equation will get,
E'=E/2.
Therefore the electric field at distance r on +q charge is E/2.
Now the force xcan be calculated at the distance r on charge +2q will be

Substitute F for
in the above equation will give,
F'=F.
Therefore, the force exert on the +2q charge at the distance r will be F.