Help on English question?

Tourists and New Yorkers alike regularly filling this theater to its 900-seat capacity.

“alike regularly filling” is underlined

A. NO CHANGE
B. alike, regularly filling
C. alike, regularly fill
D. alike regularly fill

The answer is D. Why isn’t it C? When I sound it out it sounds like there should be a comma after alike… what’s the comma rule for this situation?

The way I was always taught/understood it was that a comma is only inserted if there is a complete sentence on one side of the comma. If you split “Tourists and New Yorkers alike” and “regularly fill this theater to its 900-seat capacity” the former side is the subject whereas the latter side is the predicate. I never insert a comma unless the sentence would make sense without the section after (or before, depending on where the clause is) it. There’s probably a more technical explanation, but it works for me to understand it haha.

@jwn9917 Wow, I can’t believe I forgot that comma rule! Thanks a lot for the tip