Go to your page and click on the Variation X button.
Click on the small arrow next to the variation you want to delete and select the Delete option from the drop down menu.
If you select Variation A, you will see a different menu.
This is because our system doesn't allow you to delete the base variation of a page. You can always pause a variation if you don't want to use it.
However, if you want to get rid of it completely, you can transfer Variation B to a new page, where it will become the only variation.
In order to do this, select the Transfer option and choose New Page for This Variation.
Name your new page and click Continue.
That's it! Now you have a new page with just the variation you wanted to keep.