When two charged particles move toward each other and come to a stop, the primary forces acting on them due to their charges will continue to exert influence. In this case, the correct response is:
They accelerate in opposite directions.
Once they come to a stop, the electric force between them will cause them to accelerate away from each other if they are like charges (both positive or both negative) due to repulsion, or they will continue to attract if they are opposite charges but would likely pull closer or oscillate rather than remain stationary. However, the most straightforward response given the options is that they accelerate in opposite directions, assuming they are like charges.