Which of the following are examples of coordinate headings?

Question

A. 3, b, iii
B. A, i, a
C. ii, 2, B
D. A, B, C

My answer was C but i got it wrong,
im torn between A and B?
PLEASE HELP CANT FIND IT IN MY TEXT BOOK

Answer 1

http://papyr.com/hypertextbooks/comp1/outline.htm

I think this is what is meant by "coordinate headings."

Answer 2

A b c

Answer 3

The correct answer is D.... A B C. I just found it in my book