What do you do when you ask a question and no one wants to speak? One way to avoid this kind of situation is to make a contract with the students at the beginning of the class. Nothing they say will leave the classroom. Nothing they say will be used against them. Nothing they say can be wrong, because ti is their perspective. And keep your end of the contract, even if they test you. Making a safe environment for discussion is more important than extracting "correct" answers form the students.