If Gladys demonstrates plowing immediately before Frank demonstrates threshing, which one of the following must be true?

I don't understand how this question is possible to entertain. Through my deductions i found F cannot demonstrate threshing. This is due to F needing to demonstrate immediately before G (Rule1), and milling occurring immediately after threshing which G cannot do (Rule 3). This makes this question hard for me to wrap my head around because all of my scenarios go against what I set up. Any Help would be greatly appreciated. Thank you!