What is black's best move here?

Hi! My name is Lauren Goodkind and I’m a respected  chess coach and chess YouTuber based in California: 

https://www.youtube.com/channel/UCP5SPSG_sWSYPjqJYMNwL_Q

Black to move.  What is the best move here and why? This position was taken from a game that I recently played.  

I believe its Rg3#

Rg3#

is this a troll question?

ponz u obviously "troll" forums and posts but dont play much... correspondence is a different beast which u most likely use "book" grats... especially if ur book is an engine.. i respect lauren because she is good and kind and to be real she knows more mating patterns better than me in chess.. lots of lower rated players need to learn these mating patterns just because this is a one move mate doesn't mean it isnt an effective exercise and necessary to learn. 

Well said @prime8. A lower rated player like me appreciates what Laura does to try and help us get better.  Most higher ranked players don't care if another person gets better or not. 

Hard to beat checkmate.