Which sentence correctly uses 'needn't have' to express an unnecessary action performed in the past?

1. ক
   You needn't have bought flowers, but I appreciate it.
   
2. খ
   You needn't have to buy flowers for the party.
   
3. গ
   You needn't buy flowers since we have plenty.
   
4. ঘ
   You needn't have bought flowers if you don't want to.