Here we will use div layers to give the message on the result of the selection of the quiz. We will keep two layers one for displaying correct answer message and other for displaying wrong answer message. These two layers we will keep hidden by default. Once the correct options is clicked then the layer with correct message will be displayed. Same way for other three options we will display the layer having the wrong answer message . Read how the layers are connected to radio buttons here.
Above this line we will declare the div layers in a style sheet.
Select one option of Period button before submitting form
disabling Period button by a checkbox by using disabled property