Which identity is being used and authenticated while connection to SQL Server with Windows Authentication?

Question

SQL Server Windows authentication uses application's process identity or thread identity to connect. So, for a solution deployed to a SharePoint farm which identity will be used to connect

1. Current User Context

2. Application Pool Identity

3. Process Identity

   or another identity?!

Answer 1

It is the Application Pool Identity.

For more information, see http://technet.microsoft.com/en-us/library/cc678863.aspx

SharePoint takes care of providing appropriate permissions for this account.