The correct answer choice is B. Let's see why that's the case.
First, we need to examine the passage. In this case, we can simplify the passage into conditional reasoning. However, we need to note that the premise uses the word "tend" and the conclusion uses the word "probably"
Premise: Girls educated in single-sex secondary school - > do better academically than girls in mixed-sex schools
Conclusion: Since Alicia achieved higher grades than any other girl in first year, therefore she was probably educated in a single-sex school.
This, in essence, reverses the conditional statement. It went from A - > B, to conclude B - > A. The only thing we need to make sure is that the correct answer choice matches the passage in the strength of its conclusion and reasoning.
Answer choice B does just this.
Babies taught to swim - > have more ear infections than average.
Therefore, Janice has more ear infections than anyone else at the swim club, so she was probably taught to swim as a baby.
The exact same reversal occurs here.
I hope this helps. Please let me know if you have any other questions!