Directions: In each question you find a set of sentences arranged in a haphazard way. Choose the correct arrangement of sentences as indicated by the number to make a coherent paragraph.
A. Several other gases, such as argon, carbon dioxide, hydrogen, neon, krypton and xenon, comprise the remaining 1% of the volume of dry air.
B. Atmospheric gases hold in suspension great quantities of dust, pollen, smoke and other impurities which are always present in considerable, but variable amounts. C. The amount of water vapour and its variations in amount and distribution are of extraordinary importance in weather changes.
D. The atmosphere is a mixture of several gases.
E. Of these permanent gases, oxygen makes up about 21% and nitrogen about 78%.
F. There are about ten chemical elements which remain permanently in gaseous form in the atmosphere under all natural conditions.