Consider the Following Octahedral Complex Structures, Each Involving Ethylene Diamine

Multiple Choice

Consider the following octahedral complex structures, each involving ethylene diamine and two different, unidentate ligands X and Y. Which one, if any, of the following is a pair of optical isomers?

A) 1 and 2
B) 1 and 3
C) 1 and 4
D) 3 and 4
E) None of these choices are correct.