A. An isolated capacitor has air between its plates.
b. The capacitor is charged by a battery.
c. After the capacitor is charged, the battery is removed.
d. A dielectric slab k is then inserted between its plates.
e. Finally, the capacitor is discharged by bringing the two terminals close together, which causes a spark.

The Discharge spark will be:

i. The same as it would have been without the dielectric being inserted.
ii. Less energetic than it would have been without the dielectric being inserted.
iii. More energetic than it would have been without the dielectric being inserted.