What substance is a better oxidizing agent in each of the following pairs? Explain.

a) Co2+ or Cr3+
b) Mn2+ or I2

I think C02+ and I2 because they are above on the table.
Is this correct or do I need more information in my answer?

I think you have identified them correctly; however, I don't know which way your table goes so I don't know what above and/or below means. Written as a reduction, the potential should be more positive (less negative) and on my table the more positive values are below the more negative values.