The correct option is B Ozone layer
Ozone layer or shields is present in the startosphere, It is also called Ozonosphere. Ozonosphere lies at an altitude of 23 to 25 km over the equator and at slightly lower altitude elsewhere. Ninety percent of atmospheric ozone is present in the ozonosphere. Ozone found in the startosphere is useful for life on earth as it protects the earth from harmful ultra-violet rays and other radiations.