Are Marigolds an annual?
Yes but don't forget to take the dry dead heads off for next seasons seeding :)
Yes,and they should last being deer resistant.
To answer just your question: YES ! Yes they are an Annual.
They are annuals, only one season but pinch off spent flowers (deadheading) to promote new growth. They should snap off with a flick of your thumb. Deer and other pesky critters hate them so they should help protect your more "yummy" plants.