The student is comparing the "Inner and Outer Planets."
The reasoning behind this is as follows:
- The side with "have surface features such as mountains, valleys, and volcanoes" would refer to the inner planets (like Earth and Venus), which have solid surfaces with various geological features.
- The side with "unable to land on because there is no solid surface" refers to the outer planets (like Jupiter and Saturn), which are gas giants and do not have a solid surface to land on.
Thus, the correct response is "Inner and Outer Planets."