An AC generator may be changed into a DC generator by:

Direct current energy from a battery is transformed into mechanical energy of spinning by a d.c.motor. Maintaining the same direction of current across the load is the primary criterion for converting an AC generator to a DC generator.

After each half turn of the armature, the split ring commutator changes the direction of the current in the armature. This keeps the load's DC current flowing. As a result, choice 1 is right.