BTN bets 4bb

Heads-up Flop | BB vs BTN | 100bb effective | Difficulty: Beginner

Hero hand

2♣2♦

Board

A♥K♥9♠

Action so far:
Preflop: BTN raises 2.5bb, Hero BB calls
Flop A♥K♥9♠
Hero checks
BTN bets 4bb

Pot: 6bb   To call: 4bb

Villain range: A2s+,K9s+,Q9s+,J9s+,T8s+,AJo+,KQo

Your move: