To find the elevation of base camp, we start with Helene's initial elevation of 27 feet above sea level and subtract the distance she descends, which is 32 feet.
Calculation:
Elevation of base camp = Initial elevation - Descent
Elevation of base camp = 27 feet - 32 feet
Elevation of base camp = -5 feet
Since -5 feet is below sea level, we conclude that base camp is 5 feet below sea level.
Therefore, the correct response is:
5 feet below sea level.