In a Mailed Questionnaire,survey Researchers Often Use a Few Semi-Closed-Ended

In a mailed questionnaire,survey researchers often use a few semi-closed-ended questions.What is the purpose of including these questions?

A) To allow respondents to write in answers that do not fit the response choices
B) To demonstrate that the researcher is "open" to many possibilities
C) To permit respondents to comment further about their responses
D) To permit individuals to "talk" about their ideas in some depth