To keep dry ice in solid form, the surrounding temperature must be maintained at what level?

To keep dry ice in solid form, the surrounding temperature must be maintained at approximately -78.5°C (-109.3°F). Among the options provided, -125°F is the closest to this temperature. At this level, dry ice can remain solid without sublimating into carbon dioxide gas, which occurs at higher temperatures.

Maintaining a temperature significantly below this point, as seen in the choice of -155°F or -200°F, while not detrimental, is not necessary for the stability of dry ice. Therefore, -125°F is an appropriate temperature that ensures the dry ice remains solid during storage and handling, making it the best answer in this scenario.