Mootools select(option) not working setting attribute selected='true'

Question

Mootools

var select = new Element('select');
select.grab(new Element('option', {value: 'usd', selected: 'yes', text: 'usd',}));
select.grab(new Element('option', {value: 'usd',text: 'eur'}));

$('someContainer').grab(select);
This is the code and the selected attribute is not set. It is not set even via setPrperty by id.
Although any other attributes are set just fine. Extremely strange behaviour.

Answer 1

I go to the site mootools.net , enter the code into the console:

var select = new Element('select');
 select.grab(new Element('option', {value: 'usd', text: 'usd',}));
 select.grab(new Element('option', {value: 'usd', selected: 'yes', text: 'eur'}));

 $('header').grab(select);

At the top left of the header, a select appears with two elements. Which one is highlighted, you ask me? Second, do you know why? Because mutuls gives it a selected attribute.
Opera 11.50

Answer 2

jsfiddle.net/romanco/xpHRq/4/
yes, the select is processed, but I need the selected="true" attribute to be set, any other one is inserted, but this one is not...

Answer 3

selected="true" does not exist in principle. According to the rules, it should be selected="selected"