I believe the Answer is B but I could be wrong
In DIFFUSION AND FACILITATED DIFFUSION no energy is used. The one that needs a helper to get thing across is FACILITATED DIFFUSION.<span> Facilitated diffusion involves the diffusion of materials across the cell plasma membrane with the aid of membrane proteins such as carriers and channels. The process of diffusion does not need a carrier, the molecules to be transported just move on their own from the area of high concentration to the region of low concentration until the concentration in the space become uniform.</span>
Answer A seems like the best choice for this question. Just think about some of the synonyms for therefore—”hence,” “consequently,” and “thus.” Because the adverb therefore often plays the role of a conjunction, it's sometimes called a conjunctive adverb.
B isn’t the correct answer to this question because you use “On the other hand” to introduce two contrasting points, facts, or ways of looking at something.
C isn’t the correct answer because we are not comparing or contrasting anything in this sentence.
D isn’t the correct answer because “Especially” is used in a formal sentence example: She can't be sure she will win, especially at this early stage of the campaign.
Answer: In the control room!
Explanation: