How to display only one category in post

Good day

I need your help to solve my problem

So, what I want…I have made a screenshot of what I have now. As you can see from the image at the bottom of the post displays list of sub-categories and category.
https://imageshack.us/photo/my-images/856/73780308.jpg/

I don’t need to display the whole list of categories, I only need to show the category in what post is located, only one.

I use default twentyten theme and if I understand right this piece of code appears through twentyten_posted_in(); function.