What do you do if you don't want to re-open you're entire survey, just one or a few of the questions? You can re-open questions individually!
From the Page & Survey tab, scroll down to the Project Questions and Dynamic Content section. Closed questions will be noted in red at the bottom right corner of the question.
Locate the question you'd like to re-open, and click the gear (edit) icon on the left above it.
Click the Options menu in the upper right hand corner, and choose Re-Open Poll. Once you exit this menu, your question will be live to the public and will display on the Admin side with "open" in green at the bottom.