I can confirm that "I'm not going to be able to tell you the secret answer" was accepted by Blizzard when they locked my account and made me apply to have it unlocked.

I'm still bitter about that. I put garbage in the answer to the secret question because I planned not to forget my password. I didn't forget my password, but Blizzard nevertheless locked me out of my account, for the crime of using a payment card that was listed on my account, but wasn't listed as my "preferred" payment option.