Is it easier for the user to have all the options at a glance?

I am working on an internal webapp where we ask users about very different issues. Users have the option of not answering, but now we want to know if they really don't answer because they don't understand the question, so we want to give the option of "I don't understand the answer".

What do you think would be more user friendly? Having all the options displayed on a first screen with different buttons? Or give a button that says "skip question" and then ask the user with a pop-up?