Which of the following gases protects us from harmful sun rays?

Ozone is a very vital gas in the atmosphere. It is made up of three atoms of oxygen while ordinary oxygen is made up of only two. The ozone layer acts as a filter for the ultra-violet rays of the sun. The presence of this layer is undoubtedly a boon to humanity. In the absence of ozone in the upper atmosphere, the much harmful ultra-violet radiation would reach the earth in large amount. Such an event could lead to a disastrous consequence.