Answer:
a. The charge on C2 increases.
Explanation:
We know that voltage is divided in inverse ratio in series combination of capacitor as,
V = Q/C
The dielectric slab between the plates of C2, its capacitance will be increased as C = k£°/d
So, on inserting dielectric slab between the plates of C2, the potential difference across C2, decreases and the potential difference across C1, will now increases.