AK ip vs Flop C/R

[I KILL]

SB ($1,952)
BB ($5,000) 26/23/2.4; WTSD: 38
UTG ($596.50)
Hero ($2,921)
BTN ($1,040)

Dealt to Hero A:spade: K:club:

fold, Hero raises to $20, fold, call, call,

FLOP ($60) 9:club: 3:diamond: 4:spade:

check, check, Hero bets $10, SB calls $10, BB raises to $20, Hero calls $10, SB folds,

TURN ($110) 9:club: 3:diamond: 4:spade: 2:club:

BB bets $20, Hero calls $20,

RIVER ($150) 9:club: 3:diamond: 4:spade: 2:club: K:spade:

BB bets $20, Hero ?

was wenn River Blank?