SergeyKa, when I did the test a few weeks ago the format for the checking was find the letters or numbers which correspond to a given sequence eg:
67687 A.67678 B.67687 C.66787 D.68767 E.67667
You would obviously pick B as the correct answer.
Hope this helps
Thinking about it, although I think this is correct, I couldn't say that I'm 100% sure.