Years ago, many scholars, such as Barens, White and Lightbown, have done much research in two types of questions: closed and open-ended questions。 Closed questions are supposed to have just one acceptable answer while open questions may have a number of different acceptable answers。 This categorization is in many ways similar to that of convergent and pergent questions。 Convergent questions encourage students to focus on a central theme。 The questions typically require a single correct answer and elicit short responses from students。 Divergent questions elicit student responses that vary or perge。 There are often no right or wrong answers to pergent questions。