Answer:
C
Explanation:
The Coulomb's Law gives us the Electric Field strength of charge as follows:
E = k* (Q) / R^2
Where,
k : Coulomb constant 8.99 * 10^9 N /C
Q: Charge generating Electric Field strength
R: Distance from source to any point
In our case the value of E = 4.106 N /C is experienced by charge +3 C. This charge is replaced by an equal magnitude of charge but with negative sign -3 C. Scrutinizing on the above formula we can see that all quantities remain same hence, the magnitude of field strength remains same.
However, we also know a positive magnitude is directed away from the source charge while a negative magnitude is directed towards the source. We can conclude that only the direction of electric field reverses while magnitude remains same.