Question

which element of your work is a compelling opening statement

Answer 1

Not sure of the context of this question or what options you have available, but since you are asking in the writing group, I will answer as if you are referring to a paper. Keep in mind different classes and instructors will have different names for things so please refer to the work you have been doing in the course for the proper terminology.

All essays, theses, and other written work need an introduction. A five paragraph thesis has the following structure:

Introduction
1st body paragraph
2nd body paragraph
3rd body paragraph
Conclusion

The construction of your introduction paragraph follows a similar structure:

Opening statement (often called the Attention Getter)
Road map (comprised of three or more sentences relating to or introducing your 3 body paragraphs)
Thesis statement (not always at the end of the introduction, but usually is the best place for it since you have already introduced your talking points in the road map)

Now an Attention Getter is a compelling opening statement that makes the read want to continue reading reading your paper. It could be anything related to your topic such as an amazing statistic, a relevant and thought provoking quote, or a bold statement of your opinion. Really the possibilities are endless, it just has to hook the reader (sometimes the Attention Getter is also referred to as the Hook).

I'm not sure if this answers your question, but if not please clarify what you are asking by providing more information.