Asking professors complicated questions before or after class is generally ineffective. They are often busy during these times, so they can not give you their undivided attention. Ask if you can meet with them during their office hours to talk about the issue you want addressed. The professor may not believe that you were really sick when you have missed a number of classes. Do not only talk with your professors to complain or bring up problems.
Professors appreciate sincere compliments as much as anyone else.
Let them know when you have enjoyed learning something in their class. When you are sick or have some other problem, let the professor know as soon as possible. Asking about make-up tests before they are given will give the professor more time to work out a solution and probably cause the professor to be more sympathetic. You can communicate with your professors in many ways. Use your professor's name to humanize the discussion.