Any questions left blank will result in an RFE. The question wouldn't be asked if the Service wasn't looking for an answer.
I agree with my colleague.
You need to re-read the instructions more closely and/or consult with an attorney .. attaching a statement will be a good idea.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.
The sponsor needs to fill out the form to the fullest.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.