I am not sure about this question I tried a) but am very confused with b.

Question

Experiments were preformed with four metals and solutions of their ions: A-
A+, B-B2+, C-C2+, D-D2+. The results of the experiment were:

D2+ + C --> No reaction

B2+ + C --> B + C2+

A+ + B --> A + B2+

a)Write the equation for each reduction half reaction.

D2+ + 2e- --> D

C2+ + 2e- --> C

B2+ + 2e- --> B

A+ + 1e- --> A

b)Arrange them in a relative potential table with the easiest to reduce at the top and the hardest to reduce at the bottom.

A+ + 1e- --> A
???