Gender?

Now that the end of the school year is upon university students, the resident advisor has given the residents of the floor a survey to fill out. This survey is the ACUHO-I/EBI Resident Survey, by Educational Benchmarking, Inc., 1999. It is an international survey (at least Canadian and American), since it has a section that is only to be filled out by students at U.S. institutions. Why in the world am I talking about this survey? For section (E), the participant is supposed to fill out their gender, with the bubble-sheet options of
(A) Male
(B) Female
(C) Transgender
(D) Other

Now, I can understand the Transgender thing out of political correctness, as there are birth defects and surgeries for those things. Who, exactly, would be an "Other", if transgendered is already covered? Perhaps it is to fill space on the bubble sheet, but there are other places where spaces were left open. I'll let you figure that one out.