Which of these sentences is punctuated correctly?
Send a card to 1234 Broad St., Washington, D.C., to let us know what you think.
Send a card to 1234 Broad St., Washington, D.C., to let us know, what you think.
Send a card to 1234 Broad St., Washington, D.C. to let us know what you think.
Send a card to 1234 Broad St. Washington, D.C., to let us know what you think.
