The correct option is B older than
A comparison is being made with two friends. The comparative 'elder' is used in comparison with family members and 'older' is used when the comparison is made with friends and others. The given phrase needs to be changed to 'older than'. Hence option A is incorrect and option B is correct. Option C is incorrect because the phrase is a superlative, whereas the sentence is a comparative. Option D is incorrect because both the words in the phrase are not relevant to the statement. 'Elder' isn't used for friends, and 'to' isn't the correct comparative link.