How to delete the dropdown selected option!

Guys! can anyone help me to reslove the task. I have created a dropdown and the user can enter the option by clicking the add button the option is added in the dropdown and now the user want to delete the one of the option by selecting the dropdown option>>>

Now how can i delete the selected option!!!
Respected sir ! @ Gabor Kiss-Vamosi @ kisvegabor
help to reslove