how to reset security question
I can' t call to apple support center?
How can i reset my security Question because i forgot the answer?
I can't purchase a product ? because i need to answer the security question?
iPhone 5, iOS 7.0.2
If you have a rescue email address (which is not the same thing as an alternate email address) set up on your account then steps 1 to 5 on the page that you posted from should let you reset them : go to https://appleid.apple.com/ and click 'Manage your Apple ID' on the right-hand side of that page and log into your account, then click on 'Password and Security' on the left-hand side of that page and on the right-hand side you should see an option to send security question reset info to your rescue email address.
If you don't have a rescue email address (you won't be able to add one until you can answer 2 of your questions) then you will need to contact iTunes Support / Apple to get the questions reset.
Contacting Apple about account security : http://support.apple.com/kb/HT5699
If your countryisn't on that page then try contacting them via this page saying that you've forgottent your answers, you don't have a rescue email address, and your country isn't on the HT5699 page and see what they reply with : https://ssl.apple.com/emea/support/itunes/contact.html
When they've been reset (and if you don't already have a rescue email address) you can then use the steps half-way down the page that you posted from to add a rescue email address for potential future use