What's your move here and why?

------HAND 1------
Early William Hill £20 67 riders (15/30)
Table "Tourney 1541375 - 2" Seat 2 is the button.
Seat 1: Registrar (1450 in chips)
Seat 2: Champer5 (1445 in chips)
Seat 3: Acerclubs (3075 in chips)
Seat 5: Daes265 (720 in chips)
Seat 6: Calv10 (1900 in chips)
Seat 7: dkauto (1090 in chips)
Seat 8: Monty999 (1450 in chips)
Seat 9: enrico (580 in chips)
Seat 10: Fold'em1 (1400 in chips)
Acerclubs: posts small blind 15
Daes265: posts big blind 30
----- HOLE CARDS -----
dealt to Registrar [Qc Qh]
Calv10: folds
dkauto: folds
Monty999: folds
enrico: folds
Fold'em1: folds
Registrar: raises to 90
Champer5: folds
Acerclubs: calls 75
Daes265: folds
----- FLOP ----- [4s Ks Kd]
Acerclubs: bets 90
Registrar: ?