how do i change facebook security question ?

[Mohamed Zaalouk]

I know that this impossible , but my friend account has been hacked and the hacker changed the question itself with the answer !! so anyone knows how he have did that ? and i want also to change it because i have forget the answer i have done all things i have removed all cookies and changed my ip and changed my account password and then i have returned to my original ip then entered my e-mial and opened the e-mial from Facebook and i chooses the link that isn't me that changed the password the Facebook gave me the option to change all things except the secuirty question. this is abig hole big big hole , beacuse if someone have guessed correctly the answer he can hack the account even if i reset it . thanks in advance . sorry for my English