Scientists will continue to investigate the mystery of the yawn. Is it a leftover behavior from before humans had language? Was it a "Hey, I'm sleepy. Let's go to sleep" message? Or is it really just a way to keep our brains cool? While this behavior still is largely a mystery, one thing is certain: you are probably
fighting the urge to yawn right about now.
Which line shows the main idea of the bolded paragraph?
Scientists will continue to investigate the mystery of the yawn
O A leftover behavior from before humans had language
Was it a "Hey, I'm sleepy. Let's go to sleep message?
You are probably fighting the urge to yawn right about now