You have to allow xing2 hang2 to both be right for 行， le5 liao3 to both be accepted for 了, etc. There is NO way to tell them apart, and it's simply a matter of luck (not skill, we are developing a skill here, right???) as to whether you get it "right". Of course, these options are all right, given just a character and no context or example sentence.
This needs to be fixed.