We don’t know exactly what it means for two things to “have a few minor differences,” or whether the two sentences in question can be considered to have a few minor differences. Either way, (A) fails to point out the philosopher’s ambiguous use of the word “identical.”

This may be true, but the two sentences in question are not physically identical and the linguist argues that they are identical in meaning. So (B) doesn’t apply in the context of these two sentences.

This may be true, but it doesn’t point out the weakness in the philosopher’s argument, which is that he equates “physically identical” with “identical in meaning.”

This weakens the philosopher’s argument by pointing out his assumption that two things being “identical in meaning” is the same as two things being “physically identical.” (D) argues that the two sentences can be identical in meaning without being completely physically identical.

The philosopher is not making a claim about who has more experience with language. Instead, his argument is about the identicalness of the two sentences in question.