Which of the following is capable of reducing Eu3+(aq) to Eu2+(aq) under standard-state conditions?

Look at a table or an appendix, find the same value as (-.43V) except for each of the answers listed, and whichever one has the more negative number thats the best reducing agent, and will be able to reduce that, any one of that that has a more negative number than that of -0.43v.... should be in an appendix in any chem book