Most likely the students are using a crude measurement of time, like a stopwatch. They would get the best results with a scientific apparatus that uses a computer and optical sensors. Even recording their dropped objects with a video camera and analyzing the video would give more consistent results. Results will also vary greatly if different people are taking the time measures instead of one person making all measurements.
Eukariotic cells have nuclei, while prokaryotic cells do not.
B. Is the correct answer.
A population is all the organisms of the same species in a group, like humans. Population is different from a community in that a population is every organism of the species grouped as a whole, and a community is a certain number of organisms within the whole population. That may not make sense, but that’s as good as I can describe it.
The plant population would grow out of control