Answer :
Answer: a) C decreases; b) Q stays the same; c) E is the same
d) ΔV increase
Explanation: In order to explain this problem we have to consider the following:
C=εoA/d where A and d are the area and the separation of the plates, respectively.
Increasing d, produces a decrease of C.
Q remain constant becasuse the plates are charges and the wire are isoloted each other.
We also know that ΔV=E*d where E is electric field between the plates.
And E= Q/εo*A ( a constant between the plates)
As we can see from above, ΔV depends directely of the d so if d increase ΔV also increase. To do that we have to do work on the system.