You should begin with a chart that separates both similarities and differences. Read both articles and annotate everything you notice on to the chart. You could then begin drafting all your work and revise.
The speaker is talking about the water. During winter, the water enters the cracks and freezes and expands. It breaks the stone and makes cracks and when the water melts the holes are bigger. What he is describing is mechanical weathering which is common in nature.
The correct option is A.
From the passage given above, it can be seen that the author used the illustration of green house and its mechanism to show us the way in which the atmosphere works. The author wants us to see that just the way the glass capture the heat of sunlight and prevent it from escaping, the atmosphere works in the same manner by trapping the heat on earth preventing it from escaping, thus keeping the earth warm.<span />
