How to avoid a option from select tag

When i am selecting size,i am getting size options like this. i want to avoid size ist option(orange colored background). how to avoid that This is how i get select option

i want to avoid a size from this.

This is my select code. = select_tag "standard_size_id", options_from_collection_for_select(@standard_sizes, "id", "name"), class: ' form-control', prompt: 'Size'

Any help is appreciatable