Q:

How can I determine the sudo password?

What is the default password of the sudo? I visit some forums, it tells that the default password is password, but it doesn't work, how can I determine the password?

A:

There is no default password for sudo.  The password that is being asked,   is the same password that you set when you installed Ubuntu - the one you use to login.

A:

Sudo is asking for the user's password it's called with. In your case the password in question is the password of the user genz, hence it says [sudo] password for genz:

A:

As has been pointed out by other answers there is no default sudo password.  When you installed Ubuntu you were asked for a password it is the one you created then that you need.
The computer does not store the password anywhere but a hash value created from it; when you type a password a hash value is calculated and this is compared to the hash stored from the correct password.
This makes it very difficult to find the password.
If you have lost the password you can reset it however.  See This question
How do I reset a lost administrative password? 

