Sana is popular . . . . . . . . her friends. A. among B. by C. over D. with

The other options are incorrect because they do not accurately reflect the meaning of the sentence.

• Among means “in the company of” or “in the midst of.” In this case, it would not make sense to say that Sana is popular in the company of her friends. She is popular with her friends, not just in their company.
• By means “caused by” or “done by.” In this case, it would not make sense to say that Sana is popular caused by her friends. She is popular with her friends, not because of them.
• Over means “above” or “in control of.” In this case, it would not make sense to say that Sana is popular in control of her friends. She is popular with her friends, not in control of them.

I hope this explanation is helpful!