In the following passage some of the words have been left out. Read the passage carefully and choose the correct answer for the given blank out of the four alternatives. It so haappens that_____ siblings sing one of_____invariably has a less_____ vocal prowess even though______ have a similarly commendable ____base. siblings sing one of _______
2. The gas present in the stratosphere which filters out some of the sun's ultraviolet light and provides an effective shield against radiation damage to living things is