The correct option is A 1.4 m towards left
For the unlike charges, the net electric field is zero near smaller charge.
Let us say that the electric field is zero at a distance x from A to the left.
The electric field due to 5 C charge is 5kx2 towards left.
The electric field due to −100 C charge is 100k(x+5)2 towards right.
For the net electric field to be zero these two terms must be equal.
5kx2=100k(x+5)2
Simplifying this we get,
⇒x=5√1005−1
⇒x=1.4 m [from A towards left]