The separation between the plates of a charged parallel- plate capacitor is increased. Which of the following quantities will change ?

(a) charge on the capacitor

(b) potential difference across the capacitor

(c) energy of the capacitor

(d) energy density between the plates

Choose the correct option 

1.  (a) , (b) 

2. (b) , (c) 

3. (c) only

4. (a) , (d)