Answer:
A stronger base.
Step-by-step explanation:
In neutralization reactions, when an acid is mixed with a base, both species react to different degrees that depends on the concentrations and volumes of the acid and the base. In this case the student mixes a strong base (250 mL) with a strong acid (100 mL), what will happen is that the substance that is going to predominate (strong base) will be the one that is in greater quantity than the other, so the solution will remain a strong base.