The conclusion of the argument in this ID the flaw question is that the size and shape of a leaf fossil indicate the altitude at which that leaf grew.
Why? Because the size and shape indicate the unique climate that the plant grew in, and climate is related to altitude.
This is a tricky argument in terms of finding the gap because it seems like a great argument if you're not careful. However, notice that the size and shape of a leaf are unique to a given climate, however, each climate isn't necessarily unique to an altitude. We only know that climate "depends on" altitude. Consider that velocity of a car depends on its mass and force applied (right?), however if a car is going 100 mph, there are no doubt various combinations of mass and force that could get there, so we can't deduce the car's mass (or force applied) from speed.
(B) hinges on this issue. Perhaps multitude altitudes have the same climate.
By the way, if you were thinking about what it means if the ground rises up because of tectonic plate movements, you were ignoring that the whole argument is about where the plant grew, not where the fossil was found.
As for the wrong answers:
(A) is out of scope 00 who cares about species surviving?
(C) is pointing out that there could be other ways to "read" a leaf to figure out the climate. Who cares? We're talking about one way.
(D) analogy?
(E) is tempting if you overlooked that the whole argument is about where the plant grew. Nowhere is the location of the fossil ever discussed. Out of scope.