How do different forces act on a system

Different forces can have simillar magnitudes and same directions (but opposite), in this case the result will be nothing would happen. Or one of forces can be bigger than the other/s (in the same direction) so the system would accelerate (F=ma). Or there could be a situation with the same magnitudes but different directions, so the object (system) would accelerate in the direction of secant line (F=ma)  

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A) acceleration. this seems to be the one that makes sense.