How Marketo process the duplicate leads

Hello,

I would like to know that how Marketo will process the duplicate leads exist in the system while sending email.

For instance, a lead abc@abc.com has 3 duplicates in the system and this has been added to a batch campaign. When sending email to abc@abc.com , which record it would opt to send? and on what basis it would choose a recipient record from those 3 same email IDs. Would it send to all three?

Thanks

-Anand