This is a really difficult one. Concept check questions really do check that students have grasped a concept. Yes, that's where their name comes from! There are some difficult concepts or rather concepts that are difficult to put into words and I think truth is one of them. Apart from anything else, different nationalities have a different take on lies and truth. In some countries, not telling the truth in order to save someone's face is considered the same as telling the truth. But I don't want to get into philosophy here.
You could check students' understanding through an alternative method. Describe a scene where two teenagers, maybe brother and sister, went out and did something and they don't want their parents to know about it. You can describe what the teens did or elicit it from the students using pictures. You can invent the conversation the teenagers have with their parents the following day, include some aspects that are true and some that are not true Have the students read the conversation and to comment on where the teenagers are telling the truth and where they are not telling the truth.