Naked short call and naked short put

Which position is naked?

• A short call on 100 shares you own
• A short put with no long put below it and no cash set aside to buy the shares
• A short call with a long call one strike higher

What does the margin a broker holds against a short option tell you?

• The most the trade can lose
• The collateral the broker wants under its formula today
• The premium you will keep