Most likely due to the movement of plate tectonics. They are plates of earth under the ocean that move occasionally, over the years this is probably what happened. Plate tectonics are also the cause of most earthquakes and even tsunamis. Erosion could also play a factor in this as well.
The correct matches are as follows:
<span>1. It contains large amounts of frozen water
</span><span>C. Europa
</span><span>
2. The temperature of its atmosphere is increased by high levels of carbon dioxide
</span><span>B. Venus
</span><span>
3. It doesn't have enough gravity to have an atmosphere
</span><span>A. Earth's moon
</span><span>
4. Astronomers believe there is a good chance it contains liquid water
</span>D. Mars
Hope this answers the question. Have a nice day.