The SELECT element creates a select-list or drop-down input control.
When you specify the MULTIPLE attribute, the user may select more than
one choice by holding down the CTRL key and clicking multiple
choices.
Since a drop-down only allows one choice to be selected, when you declare
the SELECT input as MULTIPLE, it will be rendered as a select list and you
should specify the SIZE (indicating the total number of choices visible at
one time.
The end tag for this element is required.