you can select it by using the XPath //select/option[index]
.
Remember that XPath is a 1 based index by standard.
Edit After Question was updated
You can use a number of different ways to select an option from within a select. Below has been copied from the Selenium IDE on how to create option locators. To select the first item it would be index=0
select(selectLocator, optionLocator)
Arguments:
* selectLocator - an element locator identifying a drop-down menu
* optionLocator - an option locator (a label by default)
Select an option from a drop-down using an option locator.
Option locators provide different ways of specifying options of an HTML
Select element (e.g. for selecting a
specific option, or for asserting that
the selected option satisfies a
specification). There are several
forms of Select Option Locator.
* label=labelPattern: matches options based on their labels, i.e. the visible text. (This is the default.)
o label=regexp:^[Oo]ther
* value=valuePattern: matches options based on their values.
o value=other
* id=id: matches options based on their ids.
o id=option1
* index=index: matches an option based on its index (offset from zero).
o index=2
If no option locator prefix is provided, the default behaviour is to
match on label.