The correct answer is C. Consider a vote in favor of school uniforms.
Step-by-step explanation:
The purpose of a subject lin in e-mail is to inform the receiver about the general topic of the e-mail. Because of this, subject lines should summarize the content of the e-mail. Also, it is recommended to use formal language. In this context, the best option is "Consider a vote in favor of school uniforms" because this subject line shows the e-mail is about voting in favor of school uniforms, this means the subject line summarizes the content. Besides this, this is the only option that is formal as others such as "Hey, let’s put an end to the trends . . ." are too informal.