HTML Attribute for <OPTION ...>
SELECTED

SELECTED indicates that the option should be selected by default. For example, in this example, the third item ("widget analyzer") is the default item:

this code produces this select list 
<SELECT NAME="partnumber">
<OPTION VALUE="7382" >steam turbine
<OPTION VALUE="2928" >resistor array
<OPTION VALUE="3993" SELECTED>widget analyzer
<OPTION VALUE="9398" >fiber identifier
</SELECT>

(Form is not live)

SELECTED can also be used in multiple select lists. In this example, the "green team" and the "purple team" are the default selected items:

this code produces this select list 
<SELECT NAME="teams" MULTIPLE SIZE=6>
<OPTION VALUE="b" >blue team
<OPTION VALUE="g" SELECTED>green team
<OPTION VALUE="r" >red team
<OPTION VALUE="p" SELECTED>purple team
<OPTION VALUE="f" >fuschia team
<OPTION VALUE="m" >mango team
</SELECT>

(Form is not live)

<BUTTON ...> >