The correct statement about the Arenal volcano in Costa Rica is:
c. Visitors to the volcano area can participate in hiking, zip-lining, massages, and baths.
Arenal volcano has been a popular tourist destination, and many activities are available in the area. As for the other options:
a. The area is not completely closed to tourists, although there may be restrictions during periods of activity. b. The volcano was active until 2010 and has since entered a dormant phase, so this statement is partially inaccurate as it doesn't reflect the latest status up to 2023. d. While some tours might be pricey, it's not necessarily true that all visits to the Arenal volcano are extremely expensive, as there are various options available for different budgets.