My yahoo account has been blocked and yahoo is not asking me my security Q. how to open my account?

Go the Yahoo! sign in page and click on the Forgotten Password link. You will then have an option to answer the security questions you set when you created the account initially. When you complete this process, you will then be able to set a new password. Alternatively, you can request from the same Forgotten Password link that Yahoo! email you your password to the email account you gave them when you signed up. Obviously, you will need to remember which one you supplied and still be able to pick up email from that in box. If it was a Hotmail or similar webmail account, it may have expired if the account's in box wasn't popped at least once every 120 days. It would also be a good idea, if you haven't already, to update your anti virus and operating system software and ensure you have a firewall in place and that it is activated to avoid being hacked in future.