The correct answer is B. Requiring school uniforms has many advantages because students focus on their studies rather than their clothing.
Step-by-step explanation:
For a thesis statement to be effective and appropriate it is necessary in the first place that the thesis shows the position of the author towards some issue rather than just providing an opinion or stating a fact; additionally, thesis statements should be debatable which means they are not assumed as valid but arguments need to be provided and they should be specific which means they should address a point into a bigger subject and ideally state the reason or reasons related to that point.
Considering this, the best thesis statement for an essay on school uniforms is "Requiring school uniforms has many advantages because students focus on their studies rather than their clothing" this can be explained as this thesis shows the position of the author toward school uniforms that is supporting their use and also is this thesis is specific and debatable as the author provides a reason for it which is that students focus on their studies if they wear uniforms.