When teaching, give the students time to think about the questions you ask before expecting answers. Most students will not have the answer as soon as you finish asking the question. Wait about 5-10 seconds and then ask about who has an answer. Call on a student if need be.
This was one of the 5 biggest things I took away from my teaching classes. it was true in the States and it's even more true now in Korea. The students need time to translate the question and form a response in their heads. Most Korean students worry too much about speaking with perfect grammar, so be sure to let 10 seconds go by. Unlike native English speakers, most of my kids need to have their sentence formed in their head before they speak it. They will not "think out loud" and finesse their response once they get started. Some of my high level kids do this, but most do not.