To find the elevation of base camp after Helene descends 46 feet from her starting elevation of 33 feet above sea level, we can perform the following calculation:
Starting elevation: 33 feet
Descent: 46 feet
New elevation = Starting elevation - Descent
New elevation = 33 feet - 46 feet
New elevation = -13 feet
This means the elevation of base camp is 13 feet below sea level.
Therefore, the correct response is: 13 feet below sea level.