Answer:
D (proteins moving ions from low to high concentration across a cell membrane)
Explanation:
Active transport, by definition, is a type of substance transport that requires energy (typically in the form of ATP). Having said that, we can immediately eliminate B (aka water diffusion throughout the cytoplasm of a cell), as diffusion (osmosis in this case) does not require any expenditure/spending of energy. Next, we can cancel A and C because although they do require energy, there is no transport involved. Thus that leaves us with D. D is not only the answer because of the process of elimination but also b/c the ans. choice says that ions are being moved from low to high concentration, which is against the concentration gradient and thus requires energy. Hope you found this helpful! :)
A sample is a random, unbiased selection out of a larger group. An independent variable is one that is changed as to see how it will affect the dependent variable in an experiment.
Hope that helped.
