A. Is the correct answer :)
Answer:
c) Habitat isolation
Explanation:
Habitat isolation is a mechanism that prevents species from mating even if they don't have reproductive barriers. The differences in the habitat types may thus be sufficient to develop reproductive isolation between two (or more) populations
The difference between the two students that we know of is that they used a different meter stick. So the difference would be best attributed to the different tools they used.
Note, this is quite a huge difference. It's likely that one of the sticks, or both, are quite defect.
It might be stated that his reliability might be compromised because he writes the story many years later and his memories may be skewed. he is the narrator and the protagonist of the story and it is written in first person so he retells what he remembers from his life experience since he was a child.