Thank you very much for your explanations.
However I'd been confused with using of these personal pronouns till I found another one.
For those like me, I've decided to post it:
Is it "Kathryn and
I go shopping." or "Kathryn and
me go shopping." ?
The
subject pronouns must be part of the subject of the sentence; this means that the pronoun
performs the action, for example: "Kathryn and
I go shopping." Kathryn and the speaker
are performing the action of shopping, so they are the subject of the sentence.
The
object pronouns always
receive action. "The store fired Kathryn and me."
Me is the pronoun in this sentence and is correct, as opposed to "The store fired Kathryn and
I " because Kathryn and the speaker (me)
have 'received' the action of firing.