From the given table we can write following observations:
1) A is less reactive than Fe but more reactive than Cu.
2) B is more reactive than Fe but less reactive than Zn.
3) C is more reactive than Ag but less reactive than Fe, Cu and Zn.
4) D is less reactive than Fe, Cu, Zn, Ag.
Hence we can conclude that,
(i) B is the most reactive metal.
(ii) B can displace Cu as B is more reactive than Cu.
(iii) The reactivity of these metals in the decreasing order is B > A > C > D.
Reactivity series,
Zn > B > Fe > A > Cu > C > Ag > D