Just making sure it works

I've always wondered if this happened to other teachers or if I was just special. You ask a very simple question, hands shoot up, you call on a student and they give you a blank stare.  And just keep staring at you.  So you repeat the question and they continue to stare at you.  I mean it's not a wrong answer or the question was misunderstood, they literally say nothing and stare at you. Why did you raise your hand if you don't have an answer?  I just don't get it. And yes sometimes when I'm short on temper, I do ask them if they were just seeing if their hand worked. Guess what?  They stare at me when I ask that too.  And let's be honest, I'm almost always short on temper.