We can use MSN to talk with each other on the Internet.–Really Will you please show me it

It’s getting late. We must “be off” now. Which of the following can’t replace the underlined part?

I really don’t know what to about such a thing.

Help! My door shut after me and the eggs_________ in the pan.

What does the sign over there read?—”No person smoke or carry a lighted cigarette, cigar or pipe in this area．”