Which of the Following Is an Example of an Open

Which of the following is an example of an open question?

A) "Which of the following four issues do you feel is the most important problem facing this country today? If you prefer, you may name a different problem as most important; simply choose 'other' and explain your answer." (Four choices are given, plus 'other'.)
B) "Don't you think it's time that we faced the fact that unemployment is the biggest problem facing this country today?" (Choices are: yes, no, no opinion.)
C) "What do you feel is the most important problem facing this country today?" (No choices offered; participant must fill in the blank.)
D) None of the above.