You’re asking too much.
They think everyone else in the room gets it so they agree in order to not be embarrassed.
They know you aren’t talking to them.
Someone is intimidating in the room (maybe you).
They don’t know what you are talking about!
Explain what response you want. Explain how you want them to answer. For example you can say, “In a minute I am going to ask a question. I want you to think quietly about your response and then I’ll ask for 3 volunteers to share.”
Ask for a show of hands. Ask a question that doesn’t require specific answers such as, “ How many of you got 12 as your answer?”
Ask one person a direct question. Ask the question first to everyone so they all have time to think, and then call on someone. WheelDecide.com is a great tool for randomly calling on your students.
Have everyone write down a response first. This allows everyone the time to gather their thoughts and respond.
Do a Think-Pair-Share. Ask a question and have students share with a nearby neighbor so everyone has a turn to share.
Do a better check for understanding. A quick formative assessment you can try is a simple ‘Thumbs Up or Down’ if you understand. Rather than asking a question with one answer, provide an answer choice and with thumbs up or down students can agree or disagree with you.