A negatively charged particle is situated on a straight line joining two other stationary particles each having charge + q. The direction of the motion of the negatively charged particle will depend on

Concept Used: Coulomb’s law 

Detailed Solution:

According to coulomb's law,

The force acting on the charges can be mathematically represented as:

$\mathrm{F}=\frac{\mathrm{kQq}}{{\mathrm{r}}^2}$

Where r is the interparticle distance between the particle and the direction of motion of a negatively charged particle will only depend on the force acting on it, basically on the position at which it is situated.