Answer:
B. In fact
Step-by-step explanation:
The transition that would best clarify the relationship between the claim and the evidence in these sentences is option B "In fact".
This is because, according to the claim and evidence, there is a case for schools to adopt stricter dress codes because it would benefit students socially and academically, and the evidence is that school uniforms have been shown to promote school spirit and sense of belonging.
Therefore, the transition word that would be best used is "in fact", because it shows that the evidence connects with the claim.