can't i delete questions in yahoo answers?? the ones which are already resolved?? :(?

No, you can not, as stated in the Terms of Service and further covered in the help pages.

Changes to your question or answer

After posting an answer, feel free to edit or delete it up until the Asker chooses a Best Answer. A question can only be deleted before it receives its first answer.
Edit your question by clicking the Edit Menu...

https://help.yahoo.com/kb/answers/question-answer-sln4198.html?impressions=true

You can, however, disassociate yourself from your question by changing to anonymous.

Ask and Answer Anonymously

We know that there are some questions that we would rather ask and some answers we’d rather give privately. This is why we have launched the option to make your question or answer anonymous.

With this change, you can now choose to “hide” your profile from appearing next to the content after posting your question or answer. To make your question or answer anonymous, simply click “edit” and select the “make anonymous” option.

When you choose to make your question or answer anonymous, it will not appear in your history or in your network’s stream.

Note that making your question or answer anonymous will not have any effect on the content of the question or answer.

You will still get points for answering anonymously, and anonymous questions still cost points. Anonymous questions and answers are, of course, still subject to our Community Guidelines and any reported misuse of the feature will be acted upon.

http://yahooanswers.tumblr.com/post/89850099282/new-features-ahoy

You can only delete question if there is no answers.

No you can't, unfortunately Yahoo has made
some changes. Now, once answered the delete button is
removed and you can't delete your questions. Before
you have an answer, next to the add update pencil click
the x delete button.
If you are too late,emailing the YA team is no longer a possibility, several months ago they
removed the old suggest board post offering to consider doing so if questions contained personal info. Now, All
you can do is hope it is reported as a violation even resolved questions can be removed that way.

No you can no longer delete any questions that have answers. Questions are no longer considered resolved and remain open for new and fresh answers even after a best answer has been chosen.