To make sure that the child understands what you are saying, you can ask them a series of questions to see if they were listening and understand what you are saying. If they get all of these questions right, they understand what is being said. If they get only a few questions or none of them right, you need to go over what you said again and do this again.
This is a way to check that the children understand what is being said. Another way to check that they understand is to let them nod or shake their head or to ask them if they understand and let them say yes or no. This allows you to check that the children understand what is being said and lets you know if you need to go over the topic again.
